Description of the Evidence Tables

We have detailed the evidence into seven types of evidence tables, all of which are described

in detail below.  A summary table lists overall information about every trial included in our

synthesis. All two- and three-arm trials are summarized in a heading table, a continuous

outcomes table, and a discrete outcomes table. Trials with more than three arms have their results

summarized in the multi-arm heading table, multi-arm continuous outcomes table, and multi-arm

discrete outcomes table. 

At the conclusion of this description is a complete Index to Evidence Tables.  All treatments

are listed in this index, in alphabetical order, under the heading, “target arm.”  The comparison

treatment is found under the heading, “comparator arm.” The evidence, as described in Volume

1, Chapter 4 and presented in these evidence tables, provides single entries for each comparison;

these entries are ordered by Comparison Index.  The comparison is given a “secondary index” if

the comparator arm is also a  treatment of interest.

Summary Information

The Summary Table lists the trials reviewed for this report, methodological information

about the trials, and a “bottom line” summary statement abstracted from the language of the

authors. (See Volume 1, Appendix H for listing of included and excluded trials.)

In the first column, the Summary Table presents the trial number (our sequence number),

primary author, year of publication, location of trial (either as explicitly stated by the authors, or

as deduced by our abstracters based upon the author’s address), and a notation if the trial was

multi-site. This column also lists the general design of the trial: parallel (i.e., patients assigned to

different arms prospectively); matched (i.e., patients assigned to different arms prospectively, 

based on characteristics of patients already recruited); cross-over (i.e., patients receive one, then

the other treatment, in sequence); or split (i.e., patients receive both treatments at the same time). 

In the second column, the Summary Table presents the arms of the trial. These are named in

terms of the generic names of the treatments used by the investigators. Modifiers, such as

“topical,” or dosages are used in the arm names when necessary to distinguish one arm from

another within the same trial. All time points at which data were reported in the trial are listed in

this column. As was discussed in Volume 1, Chapter 2, we did not abstract all data from all time

points; so the listing in this table provides a reference to readers who wish to pursue more data

than are listed in our evidence tables.

The third column lists the total sample size plus characteristics of the participants including

combined acne severity classification (as described in Volume 1, Chapter 3), age, and gender. 

The total sample sizes were based, in most cases (243 out of the 275 trials), on data provided by

the authors on an intention-to-treat basis. In 18 trials, the authors provided sample size only on

the number of subjects completing the trial, and in 5, on subjects somewhere during the course of

the trial. In 9 trials, total sample size was provided, but the relation to the course of the study

could not be determined. The numbers of males and females listed in the third column were

derived from the best information available within the article. Because this was generally not provided on an intention-to-treat basis, the sums of males and females do not always add up to

the listed total sample size, and, in some cases, exceed it.

The fourth column lists all outcomes reported by the authors.  Not all outcomes listed here

are presented in the evidence tables.  For example, if the authors reported percentage changes in

cyst counts, we do not list both the counts and the percentage change in the evidence tables.  The

comprehensive listing in this table provides an index to reported outcomes for the interested

reader.

The fifth column lists an assessment of the methodological strengths and weaknesses of the

trial. Strengths, represented by ↑, are:

•	The report provides explicit information showing that the patients were randomized.

•	The report provides explicit information that the enroller, treatment provider, or outcomes assessor was blinded to the treatment assignment.

•	Five percent or less were lost to followup, based on patients recruited into the trial.

•	The trial is generalizable, either because the number of study centers was large or because explicit sampling methods to achieve generalizability were used.

Methodological weaknesses, indicated by ↓, are:

•	Treatment assignment was deterministic (i.e., predictable based upon a feature such as day of the week, treatment location, or digit in a medical record number).

•	Information in the report shows that patients were not blinded.

•	Information in the report shows that the enroller, treatment provider, or outcomes assessor was not blinded to the treatment assignment.

•	Data in the report show that there were major losses to followup (≥ 20 percent of recruited subjects).

•	Variable methods of outcome assessment or ascertainment were used in the various arms of the trial.

•	Subjects in the arms of the trial were not comparable.

•	The trial was not executed as designed.

The last column of the Summary Table presents an “Authors’ Bottom Line” statement that

paraphrases the conclusions made by the authors.

Presentation of Two- and Three-Arm vs. Multi-Arm Trials

The trials are broken down into two groups:

1.	Two- and three-arm trials (180 two-arm trials and 39 three-arm trials), and

2.	Trials with more than three arms (9 four-arm trials, 3 five-arm trials, 3 six-arm trials, 2 seven-arm trials, and 1 eight-arm trial). 

Group1 comprises the majority of our evidence and data. Because readers may be interested in evaluating different treatments across trials, the evidence tables are presented in terms of two-

way comparisons. Each two-arm trial reports on one two-way comparison (A vs. B). Each three- arm trial reports on three two-way comparisons (A vs. B, A vs. C, and B vs. C).  Thus Group 1  

includes a total of 297 two-way comparisons.  The 18 trials in Group 2 with more than three 

arms contribute an additional 199 two-way comparisons.  To make efficient use of space, these

are treated differently in the report.

Two and Three-Arm Trials 

The evidence tables present each comparison only once (A vs. B).  However, the index to the

evidence tables lists each comparison twice (A vs. B and B vs. A) with annotations to direct the

reader to the location of the evidence table that contains information about the 

comparison. Thus,

if topical clindamycin is compared with topical erythromycin, then the comparison may be

presented in that order in Evidence Table B, but it will be listed in two ways in the index: under

clindamycin vs. erythromycin and also under erythromycin vs. clindamycin (with an asterisk, indicating that the combination is presented in the evidence table under clindamycin).

Each of the 12 sets of evidence tables has three parts: a heading table (with ha 1  11 as a suffix), a

table of continuous outcomes (suffix 2), and a table of discrete outcomes (suffix 3, unless there

are no continuous outcomes for the comparisons, in which case the table of discrete outcomes

would have a suffix of 2).  The evidence tables are listed in order of class hierarchy and then

alphabetically by the name of target treatment in the table name.

Heading Tables

The title of the Heading Table specifies the class of the target treatment. The heading table

lists more details about the treatment administered in each trial in addition to those listed in the

Summary Table. 

The first column lists the comparison index number.  The second column lists the trial

number.  The third (target) and fourth (comparator) columns are similar.  These columns list the

component treatments in each arm including name of treatment, dose, dose units, and dose

frequency.  These columns also include comments pertaining to the entire arm.

Continuous Outcomes Tables

The following order is used within each table:

•	Trials with the same comparison index are kept together.

	•	Trials with the same name of target arm (the comparison index is repeated if the arm name changes).

		•	Trials with the same comparator arm.

			•	Outcomes in the same followup time period.

				•	Alphabetized outcome names.

Note that outcomes within arms are not grouped together; thus sometimes outcomes from the

same trial may be separated by outcomes from other trials. Outcomes are separated by a black

line while comparisons are separated by gray, thicker lines.

The first column lists abstracted information about the trial: trial number, the methodological

icons, the study design, and our Combined Acne Severity Classification for patient severity.

The second column provides the comparison index.

The third column provides our name of the outcome. Because not all outcomes reported in

the trial are listed in these tables, the reader is referred to the Summary Table for further

outcomes. The second column also reports on the body location where acne lesions were counted

(the majority type of acne outcome), if available, and provides the baseline lesion counts, if they

were provided by the authors. The baseline count provides the reader a further sense of the

severity of the acne in the trial participants.

The fourth column lists the followup duration of each outcome. As discussed in Volume 1,

Chapter 2, we discerned four time periods as relevant to acne therapy: short-term (≤ 6 weeks), mid-term (> 6 and < 12 weeks), long-term (> 12 weeks), and post-therapy (outcomes after therapy has ceased). For some outcomes, the authors were not explicit about the time frame; so

numbers may be absent from the table.

The fifth and sixth columns present the target and comparator treatment results. Because

some tables combine target treatments of similar, but somewhat different, class, the treatment

arm name is provided. Because comparator class names may change as well within the same

table, these are provided, along with the comparator treatment names.

The outcome results are provided as follows. “Percent change” indicates an outcome derived

from individual patient’s final and baseline measures, as provided by the authors. An asterisk

suffix (“Percent change*”) indicates that we had to calculate a percentage change based on

available data, meaning that it is group-based, as opposed to individual-based, when provided by the author. Individual-based is preferred, because the individual patient serves as his or her own

control. When baseline data are not provided, the outcome is “Change,” the raw difference from

baseline. An asterisk suffix (“Change*”) indicates change that we calculated. All other results are

called “Measure” and indicate outcomes with no baseline comparison. When available, the

standard deviation (“SD “) is provided. Within each treatment, a P-value is provided if it was

provided by the authors or, followed by an asterisk, if we could calculate it. These statistics are

with respect to baseline. 

The final column represents between-arm P-value of the treatment with respect to the

comparator. If no statistics were provided by the authors, we attempted to calculate P-value,

using a t-test for two samples. We could do this only when standard deviations were reported by the authors. Therefore, blanks indicate missing P-values that could not be calculated. For three-

arm trials, we selected the most relevant between-arm P-values.

Discrete Outcomes Tables

The discrete outcomes tables are ordered and structured similarly to the continuous outcomes table. They differ in the results reported. For each outcome, the outcome itself is listed, with the

number of patients who had that outcome. Because of technical reasons during trial abstraction,

an outcome with more than eight possibilities was separated into more than one outcome.

Between-arm P-values were not calculated in these tables but were included in the summaries, as manually calculated values, in those cases where we wanted to confirm a difference apparent

from the raw numbers.

Trials With More Than Three Arms

The tables for these trials parallel those for two- and arm-arm trials. Table Multi.1 is the

heading table, Table Multi.2 is the continuous outcomes table, and Table Multi.3 is the discrete

outcomes table. The outcomes are listed in a single column, rather than horizontally as pairs.

This arrangement enables readers to make their own comparison of all outcomes.