Transcript of Cyberseminar 

VIReC Database and Methods 

Measuring Laboratory Use and Results Using the VA DSS National Lab Data

Elizabeth Tarlov, Ph.D., RN, Presenter

July 9, 2012

Moderator:Welcome to VIReC Database and Method cyber seminar entitled Measuring Laboratory Use and Results Using VA Decision Support System National Extract Data. Thank you to CIDER for providing technical and promotional support for this series. Today's speaker is Elizabeth Tarlov, PhD, Associate Director of VIReC and Research Health Scientist at the HSR&D Center of Excellence here at Hines VA Hospital.  Questions will be monitored during the talk in the Q&A portion of GoToWebinar and will be presented to Dr. Tarlov at the end of her talk. A brief evaluation questionnaire will pop up when you close GoToWebinar. We would appreciate if you would take a few moments to complete it. I am pleased to welcome today's speaker, Dr. Elizabeth Tarlov.

Dr. Elizabeth Tarlov:Thank you, Margaret, good afternoon everyone. I think you know by now that today's cyber seminar toper is DSS Lab Data is a unique and very valuable resource for research. It has not been around that long, but is increasingly seen in the public literature. Recently, I did a quick lit search and found 44 published studies using DSS Lab Data in peer review journals just since 2010. And I am quite sure that I did not find them all.

Here is a roadmap for this session. We will start with an overview and then talk about how to find the information you want in the data files. I will talk about how to use the information in the files to obtain measures of laboratory use and results. Then I will have a couple of case examples to try to illustrate some of the important points I am hoping that you will take home with you today, and finally, at the end, we have additional resources that you might find useful.

But first, an audience poll I am going to, I guess I turn this over to Heidi, who operates the poll. We have a couple of questions we would appreciate your answering. The first question, "Are you currently conducting research that is using DSS Lab and/or Lab Results National Data Extracts? Yes or no." 

Moderator: We are just past 50% voted, so I am going to give it a few more seconds then I will close it out and show the results on the screen. There you go. 

Dr. Tarlov: Okay, I lost you for a moment, or I did not know where to find you. So, we have 73% nos and 27% yes, so about a quarter of the audience, in fact, has some experience with DSS Lab Data. Thank you.

The second question is, "Have you used Lab Data in CDW, the Corporate Data Warehouse, that is other than DSS data?"  

Moderator: And we will give that a few more seconds to get results in. We are about 70% right now. Okay and it looks like, in fact, about 19% of you have used Lab Data, non-DSS Lab Data in the Corporate Data Warehouse. So thank you very much, that is useful information going forward. 

Okay, so, first, to an overview of DADSS lab data. What is DSS? Well, DSS is VAs managerial cost accounting and executive information system. Its primary purpose is to provide information about productivity, cost and quality to mangers and other stakeholders. And this is important to know because the primary purpose of the data is what dictates its structure, organization, data definitions, everything about it. So understanding this central fact about DSS data is important to understanding the data you will be using and what it can tell you. This is basically a conceptual model from which the whole DSS system emanates and is designed to support. Raw materials are the labor, supplies and equipment that are used to create intermediate products. Intermediate products are the goods and services that are provided during patient care, such as x-rays, labs, nursing hours. And then the end products are completed patient care encounters, so health care providers order lab tests, x-rays, etc, for the patients' medical treatment. DSS costs the raw materials, measures intermediate product workload and cost per unit, then applies the cost to each encounter. The end result is the fully costed encounter.

It is important to keep in mind DSS does not create data. It is a derived database. It brings together data from a large number of sources and uses it to produce immediate information. And the data from which the DSS database is derived can be grouped into three principal types; financial systems that include things like payroll and building depreciation, workload data from VistA and then patient information. Every VistA system in the VA has a DSS site team, and on a monthly basis those teams are responsible for submitted their data from VistA. All of the data is then brought together and processed by DSS to create national data. And from the national data are extracted what become the national data extract. And in the front there, you see LAB and LAR which are the extracts that we are focusing on today.

The laboratory national data extract or NDE, are two of five clinical extracts. Laboratory, LAB contains workload and cost for all completed task, while the laboratory results extract contains results for a defined list of tests. And actually, that is now 91 tests. Both LAB and LAR contain test level records. So each record contains information about a single test for an individual patient. 

Clinical national data extracts also include pharmacy, radiology and event capture, QUASAR. And just to provide a little more context, other types of classes of DDEs are shown here, though we will not discuss them today. Those that contain cost related inpatient and outpatient encounters are known as the core extracts. Program activity NDEs are created to provide information on particular types of activities that is not available elsewhere. And just to mention that the health economic research center, HERC, produces technical guides on the core and some of the financial extracts. NDEs are extracts from the national data, as I mentioned. They are updated monthly or quarterly, depending on the type of the extract. Files are cumulative, year to date, and laboratory results data are available from fiscal year 2000. Lab workload and cost data are available from 2002.

NDE data are available in three formats. The first is reports and data queues available from the business support services center, BSSD. They are also available as SAS datasets at the Austin Information Technology Center on the mainframe, and finally, as SQL tables in the Corporate Data Warehouse. Note that after, at the end of this fiscal year, the SAS datasets will no longer be created or stored on the AITC mainframe. Also, note that, in fact, at this time, there are no reports or data queues that contain laboratory data in particular.

A little bit about file organization for the staff files. Data from fiscal year 2004 has a file organization that is quite different from earlier data. The fiscal year NDEs are actually a collection of files. And for each fiscal year, data for each NDEs are contained in 21 different files, corresponding to 21 VISNs, so one file contains data for one NDE, one VISN, in one fiscal year. In each of the 21 fiscal year files for LAB, and 21 files for LAR contain data for one VISN that includes inpatient and outpatient services. 

The is the current file naming convention, and I just wanted to point out here that the variables in the file names are the fiscal year, year '09, the VISN number, here 01, and then the specific NDE, known here as Lab. So, this file contains fiscal year 2009 data from facilities in VISN 1 and inpatient and outpatient data are in the same file. Fiscal year 2000 and 2003 have a different file organization, where VISNs are grouped and inpatient and outpatient data are in separate files.

DSS NDE data, as I mentioned, are also stored in the CDW. Rather than residing in staff files, the data are stored in a relational database in what are referred to as tables. The data in the CDW are available from fiscal year 2005 forward. Each NDE table contains all of the available data for that NDE. For example, there is one table that contains the lab results data for inpatient and outpatient data for all VISNs in all years. This is a new format for these searchers who have been using the SAS datasets; however, it is the same data. The data are, and after the fiscal year, will continue to be constructed just as they have been, with the same update schedule, etc. Some of the variable names are slightly different. And at the end of the presentation, in the resources section, we will provide some reference sources for more information about that.

Now, I am going to talk about what is in the data and how to find the key information. As I mentioned, first I am going to talk about the LAB NDEs here and what can be found in them. As I mentioned, the LABs are test level datasets. The LAB NDE contains records for tests performed and completed and there is one record for each completed billable test. It includes those that are performed at the point of care, so for example, if glucose is tested in the primary care clinic, that will be in the records, as well. It contains some research records. And data in the NDE identifies where and when the test is performed. It also contains cost and other information that is pertinent to accounting, and contains some limited patient information, including identifiers, so scrambled social security number and also an encounter number, birthdate, county and zip in moment priority, and a means test indicator.

Laboratory results, as the name suggests, contains test results. An extraction process selects data for those 91 tests only for extraction from VistA. And the LAR NDE also contains the patient information that I mentioned just a moment ago.

There is some important data that is not available in these NDEs and that would include diagnosing procedures and other clinical information, some demographics including gender, race and ethnicity. Tests that are not patient specific, for example, standardization procedures will not be in there. And research records are not in there unless the individual is a VA patient and an encounter was generated in the VistA Patient Care Encounter file. 

These are key test related variables, so those not related to cost. LAB has a test identifier, a variable indicating where the test was performed and also where the specimen was obtained, a referral flag indicating that the test was sent to a non-VA facility or another VA facility, a clinic stop code and dates, including the date that the test was performed and results recorded. In the LAB results NDE there are test identifiers, a result value, of course, and the unit that is recorded in and date.

I am going to talk a bit about test identifiers in both the NDEs. In the LAB NDEs there are several ways to identify records for tests you are interested in. For example, all records for a thyroxine test, I am going to give an example a little later. If you were interested in pulling all of those records for a given year, these identifiers you would use to do that. First, there is the laboratory management index program. The variable is there called VA underscore LMIP. This is a national list also known as National Lab Test Codes. The codes are entered into VistA by the lab staff and they are assigned locally, so this means that this list is not standardized across VA facilities. The CT variable is a five-digit character variable and for LAB it is usually an LMIP code. Two additional identifiers in the LAB NDE, the intermediate product number, this is assigned by DSS based on the LMIP code and notes that one IP number may be assigned to more than one LMIP or its associated feeder key. 

And finally, test names, this is a DSS derived intermediate product description. It is a free form text field. The file is maintained by the individual site team and the name assigned to the same task can vary across stations. In fact, a group of VA investigators actually looked into this variability and McGinnis et al published a paper in which they examined variability in names used by local facilities. And they found that there was greater variability in some tests than other. For example, for the hemoglobin tests, they found 116 different names across 125 facilities. So this has implications for the usefulness of the test name field. For lab tests, though, not necessarily for other types of DSS intermediate products, the IP number will generally most fully test the capture the test you want to capture.

In the lab results NDE, the DSS LARNO is the result ID. It is assigned by DSS one to 91. And there is a list of available tests on the VIReC and DSS websites. An additional identifier available in data from fiscal year 2009 forward is LOINC is a universal identifier. It is highly specific. It identifies the test, the method of analysis and the specimen source. Lab results records are pulled based on the LOINC. So, remember that I mentioned that there is an extraction process by which specific results for the 91 tests are extracted from VistA. Well, the way the records are identified for extraction are based on the LOINC code. This is a change. This was implemented nationwide for fiscal year 2009. Previously, that identification process was based on the test name. So, the use of the LOINC code for this should result in a better match between the LAB and LAR records, and just more complete record selection.

Unfortunately, the VistA LOINC file, the file that contains LOINC codes in VistA, contains an older version of the LOINC code set, and it is slated to be updated. The last we heard, this had not yet occurred, but what this means is that it is possible that some records that are intended for selection are being missed.

This is an abridged lists of tests whose results are currently extracted from VistA. These four columns are all sealed in the LAR NDE. On the left is the test number, the DSSLARNO. Then there is the test name, reporting unit, and the LOINC code or codes that are used to identify the test for extraction.

How do you find test results? Well, there is a field called results containing the results value. And it contains the result value for the particular test that is identified in the DSSLARNO field. Valid values for the results variable are negative 10,000 to 10,000, including up to four decimal digits. Some results are text or nonnumeric. And then there is a field called test units. And that is the units in which the test is reported. So you have the DSSLARNO that identifies the particular test. And when you put together the data in the results and the test unit field, you get the test results.

Here is the example from the total thyroxine. Let's say that you were interested in pulling records for results of this test in a specific period of time. You identify first of all the test ID for the total thyroxine test. That happens to be 0022. And say you are looking at a particular record. You have pulled all of the records with DSSLARN 0022. In the first record, say in the results field you see a 4.2. Continuing on in the test unit field, it says micrograms per deciliter and you sort of can concatenate those and obtain your test results, which would be 4.2 micrograms per deciliter. So the results in and of itself, alone, is an incomplete, I should say the value in the result field alone is an incomplete reporting of the results. The units are important, vital.

I mentioned that some tests are reported in text or non-numerically. This is an example for the HIV antibody test. Results are recorded descriptively rather than numerically and so a value, a numeric value has been assigned to each of the categories of test results. And so, for example, a negative or nonreactive test result for HIV antibody would appear in the record as a zero. The result field would contain a zero.

This is a common question, "Should I find a one-to-one correspondence between LAB and LAR records?" There are some scenarios where you would not expect to find a one-to-one correspondence. And one of those is for calculated variables. For those you will have a results record, but no corresponding lab record, because only the test from which the calculated values are derived are costed and so have a record in the LAB NDE. An example is creatinine clearance, which is a calculated value. You will not find an associated record for that result, rather you may find a serum creatinine record and a result associated with that, and form that the creatinine clearance is calculated.

Another situation in which you would not expect to see a one-to-one correspondence is with what are called send outs. These are when the lab is, the specimen is obtained in one facility and sent to another for analysis, or outside of the VA for analysis. In that case, two records are generated. The first record captures the in-house labor costs of specimen collection, preparation and shipping. And the second record is the cost of performing the test. In this case, the referral flag variable will have a value of Y, indicating that it was sent to another VA source.

Now we will talk about measurement of labs used in results in VA studies. And this is a case scenario example to illustrate some of the important points. This case scenario has to do with a diabetes quality of care study as an example, in which the investigators are investigating the frequency of hemoglobin A1C testing. So a typical question might be the following, "We are conducting a retrospective cohort study of care quality among patients with diabetes. We would like to measure frequency of hemoglobin A1C testing among our cohort in FY10. Should we use the LAR file, the lab results file to obtain this information? The answer to this question is no. The laboratory NDE is always the best source of information of fact of labs.

The goal of this analysis is to measure the frequency of hemoglobin A1C testing among this cohort in 2010. So I am going to go through the procedure of how you would do this as an example. As I just mentioned, you would be using the LAB file and the first step is you need to identify the test identifiers for the hemoglobin A1C test. And you do this using the feeder key and intermediate product number. It involves what is called the intermediate product table. This is a DSS table and available on the DSS intranet website in an Excel table. And what you would as a first step is to search on the name in that Excel file to obtain the associated intermediate product numbers and feeder key numbers. What you want to do is to be sure to search on all variants of the name. As I mentioned before, there can be a lot of those. Because there may be more than one record for a single intermediate product number, sometimes it can be helpful, after you search on the name, to search again, this time on the intermediate product numbers that you obtain, that you find in the records that you have found already. This is sort of an extra check in case there are records that were not picked up in your search on the test description.

Here is an excerpt from a DSS intermediate product table and in the left hand column, you will see that FDRSYS stands for feeder system. And the first thing you want to do here is limit yourself to the lab test, excuse me, the rows where the feeder system is equal to labs. In the second column, you find the intermediate product number, and then the feeder key associated with that. The CPT tick pick LMIP ECS national code indicates what kind of codes that the feeder key is from, and then finally, the description. And here, as with our example of hemoglobin A1C, you can see the variation in the name. 

The next step, you have obtained the test identifiers for the records that you want. In the laboratory national data extract, then, you, of course, want to identify the study patients' records. And then, remember, the study is examining tests in 2010. So you want to keep only the records for tests done in 2010. There are several date variables in the data. The service date tells you when the patient presented for the test, or the specimen was taken and it is expressed in eight digits for year followed by month, month and day, day. Note that there is a default should the information in the date field be missing. And that is the year and the month that the VistA extract was performed concatenated with 01 for the day. So now you have all of the FY10 records for your cohort and you want to pull the records with the feed key, or intermediate product number, equal to the values that you identified in step one using the intermediate product table.

Now, do not forget, once you do that, that you want to eliminate duplicates that might result from send or referral labs. So you identify those using the referral flag variable value equal to Y, indicates a referral and you would drop those records. Your yield, then, is all study cohort records for hemoglobin A1C tests performed in 2010. So the take home points here in this example, careful identification of the LMIP feeder key or IP number. The search that you conduct for those numbers is very study specific, but it needs to be careful and thorough. You want to watch for a date default, just be aware that those may be in the data. And then avoid over counting of records by using the referral flag to identify potential duplicates.

And take home messages about DSS LAB data and measurement issues. LAB data is really a great resource. The data are complex, and careful examination is warranted. And as is the case with all healthcare data analysis, it is important that someone familiar with lab tests, and results and processes that are involved in patient care related to labs is available to interpret what it is that you are finding in the data. 

For the final substantive section of this presentation, I am going to provide an example of DSS LAB data use from a VA study. This is a real example now. The example I am going to discuss is from a study in which I was the AMCO investigator, and in particular, the analysis that resulted in this article published in support of care in cancer. The study is called Clinical Guidelines for ESA Use in Cancer. Denise Hynes is the principal investigator of this study. It is a retrospective cohort study of patients recently diagnosed with cancer. And the study is an evaluation of prescribing behavior change following the FDA imposition of a black box warning on erythropoiesis stimulating agents. That is a bit of a mouthful. ESAs are drugs that are used to manage anemia. And for those who are not familiar, a black box warning is a type of alert that appears on the package insert for certain prescription drugs. The FDA can require it, and it indicates that the drug carries a significant risk of serious harm or life-threatening adverse effects.

This particular analysis, we addressed the question, "Does the likelihood of a cancer patients who was undergoing chemotherapy of receiving and ESA decline after the appearance of the black box warning?" This analysis was limited to lung and colon cancer patients. The outcome measure was ESA use within 12-months after diagnosis, just yes or no. and in this example, hemoglobins was a covariant in the analysis. We wanted to control for differences in hemoglobin levels that might impact the outcome.

The measurement objective was to obtain the lowest hemoglobin in the first 12-months after diagnosis, the lowest hemoglobin for each patient in the first 12-months after diagnosis. Note that there is no one right way to do this. I am sure that there are wrong ways, but unlikely to be one right way. I am going to talk about the way that we did it. We used the lab results National Data Extracts for 2002 to 2009. And we calculated the means of the two lowest hemoglobin values during the study. So, measurement issues I want to bring out here. First of all, in order to do that, we needed at least two hemoglobin test results for each patient. And we found in many cases that patients did not have two hemoglobin results in the data in the first year after their cancer diagnosis. This seems unusual since hemoglobin is a very common test. The patient has just been diagnosed with cancer. Anemia is common in cancer. However patients sometimes, or maybe often, obtain lab services outside the VA. That is one explanation for the absence of at least two values. Potentially missing VA lab data is another. 

A second issue was out of range values that we needed to drop. These out of range values could be due to lab error or processing error, data entry error. In any case, we dropped out of range values which were defined for this study based on clinical advice of a hemoglobin less than 4.0 or greater than 20.0 milligrams per deciliter. 

A third issue, there is always the potential for spurious values. This would be a value not necessarily out of range, but erroneous for not reflective of the true hemoglobin level that the patient had, for whatever reason. And it was for this reason that we chose to take the average of the two lowest values. And in that way, we minimized, or the idea was to minimize the influence of potential spuriously low values. 

And the last measurement issue involved here has to do with which two the LOINC code and FY2009 that I mentioned earlier, prior to that extraction used the test name, the test description. And this just means that there was a discontinuity in the data collection method, pre 2009 to 2009 and later. Nothing that we could do about this, but something to be aware of as we were examining the data, that the different data collection methods were used, which could have resulted in different kinds of error in the data.

That is the end of the example and the substantive portion of the presentation. I want to just go through slides here, and you have a copy of these, I think, or can obtain a copy of these. First of all, VIReC internet website resources, we have a completely redesigned internet website that was launched a couple of weeks ago. I encourage you to visit it, there are a lot of great resources. We  will intranet website up very soon in the next few days. On the website, relevant to lab data, is a DSS research user guide. There is a web page that describes the data transition, what we refer to as the data transition to the corporate data warehouse of the data. And that is an area where we will continue to post information as it becomes available about how that transition is going to be taking place, including transitioning access. And then there is a resource guide for the Corporate Data Warehouse on the VIReC website, which you will find very useful, I think.

VIReC help is also available through our help desk. And if you are not aware, we maintain a list serve called HSR Data. You can join, go to the VIReC website to find out how to find out how to join. This is a discussion among more than 650 data stewards, managers and users. You can search the archives for past messages and that can be very useful.

The decision support office website is on the VA intranet. We are not able to provide intranet URLs on the presentation, so if you do not know those and need them, you can go the VIReC intranet website and the URL will be available there. The decision support office website has multiple resources that are critical for using the data. These include a National Data Extract Technical Guide, NDE layout specifications and that will include the sequel table layout. And you can find those all by clicking on national reporting in the left navigation pane. 

Two additional VA intranet websites that you will undoubtedly find useful is the CDW Share Point site and the Da Vinci Share Point site. And I think that is the end of my presentation. And we have time for questions.

Moderator:Great, thank you, Elizabeth. There are quite a few questions. The first one, "If staff file storage will be stopped in Austin, where will they be stored in the future?

Dr. Elizabeth Tarlov:This is a good question, and the answer is unclear. This is one of the things that I will refer you to the VIReC webpage on the transition. The information is not currently available. Frankly, we have received different answers to that question at different times, from different offices. It is not clear that the SAS datasets will be available at all, but again, that is not clear. So we promise to disseminate the information as we obtain it.

Moderator:Okay, "Can you recommend any books or online resources for someone who has never used SQL before?"

Dr. Elizabeth Tarlov:Another common question at this time. SQL is a programming language for relational database management. It is not like SAS for statistical analysis. And there are a few simple, simple statements that we will all learn that will allow us to extract the SQL data and transform the data into a SAS dataset for analysis. There is a best practices guide on the CDW Share Point site that describes how to do that.

Moderator:Okay. "Does the LAR include the normal range for tests, since tests performed at different Vas may have different reference ranges?"

Dr. Elizabeth Tarlov:Good point, no. The data do not contain the reference ranges.

Moderator:"Can you give the reference for the paper just mentioned on test name variability?" That was on the hemoglobin test, I think, name variability.

Dr. Elizabeth Tarlov:Sure. The first author on that paper, the last name, I am sorry, I do not remember the first name. The last name is McGinnis, I think, published in 2010. 

Moderator:Okay, "Are the tests listed on slide 29 inclusive of all tests that are currently stored?" that was your list of FY11 LAR tests, abridged.

Dr. Elizabeth Tarlov:Oh, no, there are 91 tests, and that was just an example.

Moderator:Okay, "Is the lab – 

Dr. Elizabeth Tarlov:Excuse me.

Moderator:Sorry.

Dr. Elizabeth Tarlov:The complete list of tests is available on the, there is a list on the VIReC website complete for the 89, I believe. And on the DSS website you will find all 91 tests. And let's see, before I stop here, I just want to get back to the question on the McGinnis paper, because I realized I have the citation here. So the first, the initials are K.A., so K.A. McGinnis. It appeared in *Medical Care* in 2009. Volume 47, Issue No. 1, and it is called *Comparison of Two VA Lab Data Repositories Indicates that Missing Data Varies, Despite Originating From the Same Source.*.

Moderator:The next question, "Is LAB CHEM data available in DSS?"

Dr. Elizabeth Tarlov:Well, I am not sure exactly what the questioner means. I know that there is a domain in CDW that contains the LAB data called LAB CHEM. All completed tests, with the exceptions that I mentioned, will be in the LAB NDE, there will be a record for those. Test results, however, will only be in the LAR for tests that are on that list of 91.

Moderator:Okay, "Why can't you use the LAR file for A1C tests? Is there some limitation of LAR that makes it inappropriate for measuring frequency as well as value of tests?"

Dr. Elizabeth Tarlov:Yeah, if you – the value is a different story, if what you need is result values, obviously, that is only found in the LAR NDE. However, if what you are doing makes it important that you capture all of the specific tests, you want to use the LAB NDE. And the reason for that is remember that the LAB NDE captures, records workload and cost. And so it will contain every record. The results, however, have potential data processing issues related to them that I mentioned. One, before 2009, tests were extracted based on the test name. If the test name, remember that th3ese things can be altered locally by the site team, and if the test name was changed for whatever reason in the local VistA system, then the program that was extracting, based on the other test names, will fail to pick up that record. Similarly, with LOINC codes, well, it is not that same problem, no problem with the missing a record with that LOINC code. But as I mentioned, the LOINC code file in VistA is not up to date. And so let's say that there is a test that is identified by a LOINC code that is a newer code, and that code is not available in VistA. Well, clearly, then, any record identified by that LOINC code will not be identified and extracted into the LAR data. So, for reasons like that, and you need to capture all tests, you want to use the LAB NDE.

Moderator:Next question: "From slide 38, I heard we should take feeder key for all feeder system equal labs for variations of the description for a test; why are we not considering the feeder system equals ASC as well?"

Dr. Elizabeth Tarlov:To be honest, I do not have a complete answer for this question, and I would be happy to get a complete answer and provide it. However, I believe that records where the feeder system is identified by ASC records some workload. Those are codes for the workloads that have to do with the services that surround the encounter, that are involved in the encounter and do not denote the lab tests per se. So lab records come from the laboratory. However, as I mentioned, I feel like I do not have a complete answer for that. and so I will get that and make it available through Heidi.

Moderator:Okay, "Can you provide the issue and page number for the trends in anemia management article in support of care in cancer?"

Dr. Elizabeth Tarlov:It was published online ahead of print last September. And I think I got a message just very recently, in the last couple of days, maybe even this morning, it seems so long ago, that in fact it was published in print. So I believe it is in the current issue.

Moderator:Okay, thank you. Okay, next one, "Great presentation, are there any VA studies planned to look at the hemoglobin A1C by gender? How would this data be available?"

Dr. Elizabeth Tarlov:Whether or not there are any studies looking at that, I do not know. And I did not talk about data access at all today. That information is available on our internet website, but basically it would be a matter of obtaining access to the data and the rules around that vary depending upon whether the project is for research or VA operations. So I refer you to the VIReC internet website.

Moderator:Next question, "What are the core difference between the DSS LAB/LAR data and the CDW LAB dat?"

Dr. Elizabeth Tarlov:CDW LAB data is – I am going to give a description here that may, that in terms – technically it details not the way that it would be described by a CDW person or a database person. But, CDW data is a complete, unedited mirror, basically of what is in VistA. And it will contain the data are back to 1999, I believe. And it will contain all tests done, all results for the tests, and unlike DSS, which again is a derived database, there are specific variables that are there for part of the primary purpose of the data and there is some editing that goes on. Again, I refer you to the CDW Share Point site that will describe what is available there in more detail.

Moderator:Okay, we are just about at the top of the hour. There is one last question here, "Will no med codes be used in the CDW?"

Dr. Elizabeth Tarlov:I am afraid I cannot answer that question. I do not have the answer. However, again, I refer you to the CDW Share Point site and/or to the VIReC desk, and we would be happy to assist you in finding the answer to the question.

Moderator:Okay, thank you very much, Dr. Tarlov. Thank you, audience, I want to remind you to fill out the questionnaire when you lot out. Our next session is scheduled for Monday, August 6th, 1:00 to 2:00 p.m. eastern time, and is entitled *Improving Mortality Ascertainment Using the VHA Vital Status File.*" Thank you all.

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