**Limited Access Dataset for**

**Aspirin Myocardial Infarction Study (AMIS)**

**Final Report**

**Maryland Medical Research Institute**

**600 Wyndhurst Ave.**

**Baltimore, MD 21210**

**October, 2004**

**Table of Contents**

1\. Introduction

2\. Computer Files

3\. Modifications for Limited Access Data Set

a.  Dataset and structure

b\. Variable Naming Scheme

c\. Data Modification

d\. Winsorizing

4\. Dataset Format

5\. Appendix

a.  Data Dictionary

b.  Code Book

c.  Comparison of Selected Variables from Original data source with
    Modified dataset

d.  Frequencies and means of Selected Variables from Initial Visit and
    Baseline

e.  Frequencies and means of Selected Variables from death and non-fatal
    events.

f.  Frequencies and means of Selected Variables from 3 annual follow-up
    visits

Introduction

This document provides an overview of the data available for the Aspirin
Myocardial Infarction Study (AMIS), which collected data from 1975-1979.
The original data was published in an ASCII data format. It has been
updated to SAS file format. Changes have also been made in accordance
with the winsorizing procedure.

## 

## Computer Files

The following table lists the files on this CD-ROM and their contents.

+-----------+----------------------+-----------------------------------+
| ###       | #### File Name       | #### Contents                     |
| # Folder  |                      |                                   |
+-----------+----------------------+-----------------------------------+
| Document  | Instruction.doc      | Data processing document          |
+-----------+----------------------+-----------------------------------+
|           | DataDictionary.doc   | Dataset structure and format      |
+-----------+----------------------+-----------------------------------+
|           | CodeBook.doc         | Data format and values            |
+-----------+----------------------+-----------------------------------+
|           | AMIS book.pdf        |                                   |
+-----------+----------------------+-----------------------------------+
|           | Resting ECG Coding   |                                   |
|           | system.pdf           |                                   |
+-----------+----------------------+-----------------------------------+
|           | Publications.pdf     | AMIS JAMA article                 |
+-----------+----------------------+-----------------------------------+
|           | Stat_Baseline.doc    | Frequencies & means of selected   |
|           |                      | variables from initial visit and  |
|           |                      | baseline                          |
+-----------+----------------------+-----------------------------------+
|           | Stat_Event.doc       | Frequencies & means of selected   |
|           |                      | variables from death and          |
|           |                      | non-fatal events                  |
+-----------+----------------------+-----------------------------------+
|           | Stat_Followup.doc    | Frequencies and means of selected |
|           |                      | variables from 3 annual follow-up |
|           |                      | visits                            |
+-----------+----------------------+-----------------------------------+
|           | Comparison.pdf       | Comparison of selected variables  |
|           |                      | from original data source with    |
|           |                      | modified data                     |
+-----------+----------------------+-----------------------------------+
| Dataset   | Baseline.sas7bdat    | Limited access dataset of initial |
|           |                      | visit and baseline for SAS        |
|           |                      | Windows version (without format   |
|           |                      | for variables)                    |
+-----------+----------------------+-----------------------------------+
|           | Events.sas7bdat      | Limited access dataset of death   |
|           |                      | and non-fatal event for SAS       |
|           |                      | Windows version (without format   |
|           |                      | for variables)                    |
+-----------+----------------------+-----------------------------------+
|           | Followup.sas7bdat    | Limited access dataset of 3       |
|           |                      | annual follow-ups for SAS Windows |
|           |                      | version (without format for       |
|           |                      | variables)                        |
+-----------+----------------------+-----------------------------------+
|           | Base_Fmt.sas7bdat    | Limited access dataset of initial |
|           |                      | visit and baseline for SAS        |
|           |                      | Windows version (with format for  |
|           |                      | variables)                        |
+-----------+----------------------+-----------------------------------+
|           | EventFmt.sas7bdat    | Limited access dataset of death   |
|           |                      | and non-fatal event for SAS       |
|           |                      | Windows version (with format for  |
|           |                      | variables)                        |
+-----------+----------------------+-----------------------------------+
|           | Folw_Fmt.sas7bdat    | Limited access dataset of 3       |
|           |                      | annual follow-ups for SAS Windows |
|           |                      | version (with format for          |
|           |                      | variables)                        |
+-----------+----------------------+-----------------------------------+
|           | AMIS_v6.xpt          | AMIS limited access data file in  |
|           |                      | SAS transportable format for SAS  |
|           |                      | Version 6. (Including all 6       |
|           |                      | datasets)                         |
+-----------+----------------------+-----------------------------------+
|           | AMIS_v9.xpt          | AMIS limited access data file in  |
|           |                      | SAS transportable format for SAS  |
|           |                      | Version 9. (Including all 6       |
|           |                      | datasets)                         |
+-----------+----------------------+-----------------------------------+
|           | Formats              | SAS Format catalogue for all 3    |
|           |                      | datasets                          |
+-----------+----------------------+-----------------------------------+
| Program   | AMIS_Format.sas      | SAS code for data formats         |
+-----------+----------------------+-----------------------------------+

## 

## Modifications for Limited Access Data Set

a.  **Datasets and structure**

> The original AMIS data set contained one observation per subject. Each
> observation contained data from an initial visit, a baseline visit,
> three follow-up visits, three missed visits, lab data, and event data.
> For the convenience of data management and space wise consideration,
> we have divided the entire data into three datasets.

1.  Baseline: This dataset includes all initial visit, baseline visit
    and labs, and ECG data. There is one record for each subject. Total
    4524 records are in this dataset.

2.  Events: This dataset includes all death and non-fatal events data
    collected during the study. There is one record for each subject.
    Total 4524 records are in this dataset.

3.  Follow-ups: This includes three annual visit data of exam and labs.
    The same variables were collected for each follow-up visit.
    Therefore, 3 records per subject and total 13572 records are
    included in this dataset. Each visit is identified by the visit
    number:

> Visit=1 indicates the 1^st^ annual visit which was the 4^th^ visit
> during the study;
>
> Visit=2 indicates the 2^nd^ annual visit which was the 7^th^ visit
> during the study;
>
> Visit=3 indicates the 3^rd^ annual visit which was the 10^th^ visit
> during the study.

b.  **Variable Naming Scheme**

    1.  The variable naming scheme is based on the forms from which the
        variables were obtained, as well as the question number on the
        form (e.g. 'bl19' is baseline form question 19). If the question
        on the form is conditional on the last question or is part of a
        series of questions listed under one number, a letter is added
        after the number in the variable name. Numbers and letters
        alternate for each level of hierarchy, regardless of whether
        number or letters were used on the form (e.g. fv26a1).

> The following are the prefix codes used for the variables:

+----------------+-----------------------------------------------------+
| **Prefix**     | ### Description                                     |
+----------------+-----------------------------------------------------+
| iv             | initial visit form                                  |
+----------------+-----------------------------------------------------+
| bl             | baseline visit form                                 |
+----------------+-----------------------------------------------------+
| dn             | death notification form                             |
+----------------+-----------------------------------------------------+
| la             | lab data (no form)                                  |
+----------------+-----------------------------------------------------+
| ecg            | ecg data (no form)                                  |
+----------------+-----------------------------------------------------+
| fv             | follow-up visit form                                |
+----------------+-----------------------------------------------------+
| mv             | missed visit form                                   |
+----------------+-----------------------------------------------------+
| nf             | non-fatal event (no form)                           |
+----------------+-----------------------------------------------------+

> The following variables were not on any form or did not have a
> question number and were named based on description:

  -------------- ------------------------ -------------- -----------------------------
  **Variable**   **Description**          **Variable**   **Description**

  id             patient identifier       iucod          important underlying cause of
                                                         death

  trtgrp         treatment group          cucod          contributing underlying cause
                                                         of death

  invex1         follow-up visit form:    cdiimod        important immediate mechanism
                 attended visit 1                        of death

  invex2         follow-up visit form:    cimod          contributing immediate
                 attended visit 2                        mechanism of death

  invex3         follow-up visit form:    visit          visit number
                 attended visit 3                        

  age            age at randomization     fvrev          follow-up visit form revision
                                                         number

  vitstat        vital status             mvrev          missed visit form revision
                                                         number
  -------------- ------------------------ -------------- -----------------------------

2.  Some questions were revised in later form revisions. The
    corresponding variables were split into two variables, with 'i'
    appended to the variable name containing the revision 1 data and
    'ii' appended to the variable containing revision 2 data. The
    variables 'fvrev' and 'mvrev' list the revision number.

3.  The variables 'iv13' and 'bl08' have corresponding variables 'iv13a'
    and 'bl08a' indicating that the year was uncertain. These should be
    taken into account when using 'iv13' or 'bl08'.

# **Data Modification**

> Missing values are indicated by '.' or a blank space (character
> variables). All values for which the coding changed in subsequent
> revisions were recoded to conform to revision 2 coding. Lab values
> were converted to gravimetric units. Height was converted to inches.
> Some continuous variables had coded values in addition to the normal
> range of the variables. These variables were split into two: the first
> contains the usual range; the second contains the coded values, and an
> 'i' was appended to the second variable name. Date variables in which
> the month or day were unknown were changed to 6 and 15 respectively in
> order to calculate time-to-event.

# 

# **Winsorizing**

i.  Extreme values in the following variables were collapsed to a
    single, mean, extreme value:

+-------+------------------+-------------+-------------+-------------+
| **    | **Description**  | **Remaining | #### Mean   | **Mean High |
| Varia |                  | Range**     | Low Extreme | Extreme**   |
| ble** |                  |             |             |             |
+-------+------------------+-------------+-------------+-------------+
| age   | age at           | 35-65       | 32          | 68          |
|       | randomization    |             |             |             |
+-------+------------------+-------------+-------------+-------------+
| iv16  | no. of MI's      | 1-3         | n/a         | 4           |
|       | patient ever had |             |             |             |
+-------+------------------+-------------+-------------+-------------+
| bl35  | height (inches)  | 60-77       | 58          | 79          |
+-------+------------------+-------------+-------------+-------------+
| bl36  | weight: baseline | 110-240     | 105         | 255         |
|       | (lbs.)           |             |             |             |
+-------+------------------+-------------+-------------+-------------+
| bl37a | SBP: baseline    | 100-170     | 94          | 180         |
|       | (mm/hg)          |             |             |             |
+-------+------------------+-------------+-------------+-------------+
| bl37b | DBP: baseline    | 60-100      | 54          | 106         |
|       | (mm/hg)          |             |             |             |
+-------+------------------+-------------+-------------+-------------+
| fv36  | weight:          | 110-240     | 105         | 255         |
|       | follow-up (lbs.) |             |             |             |
+-------+------------------+-------------+-------------+-------------+
| fv37a | SBP: follow-up   | 100-170     | 64          | 180         |
|       | (mm/hg)          |             |             |             |
+-------+------------------+-------------+-------------+-------------+
| fv37b | DBP: follow-up   | 60-100      | 54          | 106         |
|       | (mm/hg)          |             |             |             |
+-------+------------------+-------------+-------------+-------------+

ii. Uncommon values in the following variables were recoded as 'other':

  --------------- -------------------------------------------------------
  **Variable**    **Description**

  iucod           important underlying cause of death

  cucod           contributing underlying cause of death

  cdiimod         important immediate cause of death

  cimod           contributing immediate cause of death
  --------------- -------------------------------------------------------

iii. All collapsed variables have an additional corresponding variable
     with a 'c' appended to the variable name, coded 1 for collapsed and
     0 for actual value (e.g. bl37bc).

iv. All dates were deleted and new variables were calculated as 'age at
    event' or 'days in study until event'.

v.  The following identifying variables were deleted from the data set:

  -------------- ------------------------- -------------- ----------------------------
  **Variable**   **Description**           **Variable**   **Description**

  iv04           birth date                nf04i          angina pectoris: reason for
                                                          no date

  clinic         current clinic            nf07           cardiovascular surgery:
                                                          follow-up date that
                                                          procedure was reported

  bl60           randomization date        nf08           cardiovascular surgery: date
                                                          of follow-up exam

  la01           date specimen received:   nf08i          cardiovascular surgery:
                 baseline                                 reason for no date

  la02           date specimen received:   nf11           coronary arteriography:
                 exam 4                                   follow-up date that
                                                          procedure was reported

  la03           date specimen received:   nf12           coronary arteriography: date
                 exam 7                                   of follow-up exam

  la04           date specimen received:   nf12i          coronary arteriography:
                 exam 10                                  reason for no date

  fv29a          last completed visit date nf15           heart failure: follow-up
                                                          date that event was reported

  fv29b          capsules prescribed per   nf16           heart failure: date of
                 day at last visit                        follow-up exam

  fv29c          present visit date        nf16i          heart failure: reason for no
                                                          date

  fv29d          capsules prescribed per   nf19           ICIA: follow-up date that
                 day at present visit                     event was reported

  fv29e1         prescription date         nf20           ICIA: date of follow-up exam

  fv29e1a        no. of capsules           nf20i          ICIA: reason for no date
                 prescribed                               

  fv29e2         prescription date         nf23           intermittent claudication:
                                                          follow-up date that event
                                                          was reported

  fv29e2a        no. of capsules           nf24           intermittent claudication:
                 prescribed                               date of follow-up exam

  fv29e3         prescription date         nf24i          intermittent claudication:
                                                          reason for no date

  fv29e3a        no. of capsules           nf27           myocardial infarction:
                 prescribed                               follow-up date that event
                                                          was reported

  fv29e4         prescription date         nf28           myocardial infarction: date
                                                          of follow-up exam

  fv29e4a        no. of capsules           nf28i          myocardial infarction:
                 prescribed                               reason for no date

  fv30b          reason for reduced        nf31           peripheral arterial
                 prescription                             occlusion: follow-up date
                                                          that event was reported

  fv30c          reason for reduced        nf32           peripheral arterial
                 prescription                             occlusion: date of follow-up
                                                          exam

  fv30d          reason for reduced        nf32i          peripheral arterial
                 prescription                             occlusion: reason for no
                                                          date

  fv30e          reason for reduced        nf35           pulmonary embolism:
                 prescription                             follow-up date that event
                                                          was reported

  fv44a          date urine specimen       nf36           pulmonary embolism: date of
                 collected                                follow-up exam

  fv50a          projected date interim    nf36i          pulmonary embolism: reason
                 urine salicylate                         for no date
                 determination                            

  fv51a          date blood specimen       nf39           stroke: follow-up date that
                 obtained                                 event was reported

  mv10a          approximate date          nf40           stroke: date of follow-up
                 discontinuation                          exam

  nf03           angina pectoris:          nf40i          stroke: reason for no date
                 follow-up date that event                
                 was reported                             

  nf04           angina pectoris: date of  fv10d          Event since last visit:
                 follow-up exam                           peripheral arterial
                                                          occlusion

  fv10a          Event since last visit:   fv10e          Event since last visit:
                 MI                                       cardiovascular surgery

  fv10b          Event since last visit:   fv10f          Event since last visit: GI
                 stroke                                   disorder require
                                                          hospitalization

  fv10c          Event since last visit:   fv10g          Coronary arteriography
                 pulmonary embolism                       
  -------------- ------------------------- -------------- ----------------------------

4.  **Dataset Format**

> The included AMIS limited access data files were created using two
> different methods. The first (found in all \*.sas7bdat dataset) are PC
> SAS datasets created using SAS for Windows Version 9.0. The second
> (found in all \*.xpt datasets) are SAS transport files created using
> SAS export engine with PROC COPY. Some variable labels may have been
> truncated in the transport data files. The details of variable
> descriptions can be found in the data dictionary.
>
> All datasets with no 'Fmt' on the name does not contain formats for
> the variables. AMIS_Fomat.sas contains a SAS program to insert the
> labels and formats for all variables if these dataset were used.
>
> When the datasets were used with a lower Version of SAS system, the
> text of variable labels and format might be truncated per the limit of
> that version. This might also invoke an error message displayed on the
> SAS log file, but will not affect the data values.

**5. Appendix**

a.  Data Dictionary

b.  Code Book

c.  Comparison of Selected Variables from Original data source with
    Modified dataset

d.  Frequencies and means of Selected Variables from Initial Visit and
    Baseline

e.  Frequencies and means of Selected Variables from death and non-fatal
    events.

f.  Frequencies and means of Selected Variables from 3 annual follow-up
    visits