Effective Use of the RETAIN Statement in Programming Clinical Trial

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Effective Use of the RETAIN Statement in Programming

Clinical Trial

Mingxia ChenBiostatisticianBeijing, China


Introduction

• RETAIN statement causes a variable that is created by an INPUT or assignment statement to retain its value from one iteration of the DATA step to the next ---- SAS help document

• In contrast to the default DATA step behavior, without RETAIN statement, SAS automatically sets new variables in the data step to missing at the start of each iteration

• The RETAIN statement is very useful to perform data manipulation across observations.

• RETAIN is simpler and more flexible, to speed up your program.


Example 1

Concatenate character values from multiple records of the same variable


Original Dataset (SUPPEX)

Result Dataset (REASON)

USUBJID IDVARIDVARVAL

QNAM QLABEL QVAL

100-5001 EXSEQ 1EXLOT1

Lot Number 1 583918


Lot Number 2 590118


Lot Number 3 598303

100-5001 EXSEQ 2 IIREASReason for injection interruption

Adverse Event

100-5001 EXSEQ 2 IISPEC Specify for interruptionALLERGIC REACTION, SKIN RASH, DYSPNEA


Lot Number 1 540327


Lot Number 2 558160

…… …… …… …… USUBJID EXSEQ EXLOT REASON

100-5001 1583918, 590118, 598303

　

100-5001 2 　 Adverse Event: ALLERGIC REACTION, SKIN RASH, DYSPNEA

100-5002 2 540327, 558160 　

…… …… …… ……

　　　


Original Dataset (SUPPEX)

Result Dataset (RSLTDS)

100-5001 EXSEQ 2 IIREAS Reason for injection interruption Adverse Event

100-5001 EXSEQ 2 IISPEC Specify for interruption ALLERGIC REACTION, SKIN RASH, DYSPNEA

USUBJID

IDVAR

IDVARVAL

QNAM QLABEL QVAL

100-5001

EXSEQ

1EXLOT1

Lot Number 1 583918

100-5001

EXSEQ

1EXLOT2

Lot Number 2 590118

100-5001

EXSEQ

1EXLOT3

Lot Number 3 598303

100-5002

EXSEQ

2EXLOT1

Lot Number 1 540327

100-5002

EXSEQ

2EXLOT2

Lot Number 2 558160

…… …… …… ……

USUBJID EXSEQ EXLOT REASON

100-5001 1 583918, 590118, 598303 　

100-5002 2 540327, 558160 　

…… …… …… …… 　　　


PROC SORT DATA=SUPPEX; BY USUBJID IDVAR IDVARVAL QNAM;RUN;DATA RSLTDS(KEEP=USUBJID EXSEQ EXLOT REASON); SET SUPPEX; BY USUBJID IDVAR IDVARVAL QNAM; FORMAT EXLOT REASON $200.; RETAIN EXLOT REASON; IF FIRST.IDVARVAL THEN DO; EXLOT=""; REASON =""; END;

IF INDEX(QNAM,“EXLOT")>0 THEN EXLOT=CATX(“, ", OF EXLOT QVAL); IF QNAM IN (“IIREAS", “IISPEC") THEN REASON=CATX(": ", OF REASON

QVAL);

IF LAST.IDVARVAL;

EXSEQ=INPUT(IDVARVAL, best.);RUN;

SAS Code

Assigns initial value (missing) to EXLOT, REASON

Prevents the 2 variables from being reset to missing for each iteration.

Concatenates character values of QVAL in multiple records

Keeps the last observation per SUBJECT per EXSEQ


Example 2

Select the previous minimum sum of longest diameters in oncology clinical trials


Original dataset (TR)USUBJID

VISITNUM

VISITTRTESTCD

TRTESTTRSTRESN

TRSTRESU

100-5001 -1 PRE-TREATMENT SUMLDIAMSUM OF LONGEST DIAMETER

74 mm


94 mm

100-5002 110 TUMOR ASSESSMENT 1

SUMLDIAMSUM OF LONGEST DIAMETER

84 mm



92 mm



106 mm


96 mm



100 mm



95 mm


188 mm

101-5002 110TUMOR ASSESSMENT 1


65 mm



66 mm



66 mm



63 mm



61 mm

…… …… …… ……


Result Dataset (PREMINSL)USUBJID

VISITNUM

VISITTRTESTCD

TRTESTTRSTRESN

TRSTRESU

PREMIN

SL 100-5001

-1 PRE-TREATMENTSUMLDIAM

SUM OF LONGEST DIAMETER

74 mm .

100-5002



94 mm .

100-5002

110 TUMOR ASSESSMENT 1

SUMLDIAM


84 mm 94

100-5002


SUMLDIAM


92 mm 84

100-5002


SUMLDIAM


106 mm 84

100-5005



96 mm .

100-5005


SUMLDIAM


100 mm 96

100-5005


SUMLDIAM


95 mm 96

101-5002



188 mm .

101-5002

110TUMOR ASSESSMENT 1

SUMLDIAM


65 mm 188

101-5002


SUMLDIAM


66 mm 65

101-5002


SUMLDIAM


66 mm 65

101-5002


SUMLDIAM


63 mm 65

101-5002


SUMLDIAM


61 mm 63

…… …… …… ……


SAS CodePROC SORT DATA=TR; BY USUBJID TRTESTCD VISITNUM;RUN;

DATA PREMINSL(DROP=LASTSL); SET TR; BY USUBJID TRTESTCD VISITNUM;

RETAIN PREMINSL ;

LASTSL=LAG(TRSTRESN);

IF FIRST.TRTESTCD THEN DO;

LASTSL=.;

PREMINSL=.;

END;

ELSE PREMINSL=MIN(PREMINSL, LASTSL);

RUN;

Prevents PREMINSL from being reset to missing for each iteration

Sets LASTSL to missing for the first visit of each SUBJECT

LAG function to Get the value of the last observation

Sets PREMINSL to missing for the first visit of each SUBJECT

Compares PREMINSL to LASTSL in current iteration and resets value if LASTSL is smaller


Example 3

Count the number of observations (example AE table summary)


AE Summary Table


Analysis Dataset (ADAE)TRTAN USUBJID AESEQ AETERM TEAEFL TESAEFL RTEAEFL

A 100-5001 1 CHEILITIS 　　　

A 100-5001 2 CONSTIPATION Y 　　



A 100-5001 5 DIARRHEA Y 　　

A 100-5004 1 BACK PAIN (THORACAL) Y 　 Y

B 100-5002 1 ANEMIA Y 　　

B 100-5003 1 FEVER WITH CHILLS Y 　　

B 100-5003 2 NAUSEA Y 　　

B 100-5003 3 PNEUMONIA Y 　 Y

B 100-5005 1 ASYMPTOMATIC PULMONAL EMBOLE 　　　

B 100-5005 2 LOSS OF APPETITE Y 　 Y

B 100-5005 3 NAUSEA Y 　　

B 100-5005 4 NEUTROPENIA Y 　　

B 100-5005 5 NEUTROPENIA Y 　　

B 100-5005 6 PAIN LEFT ILIAC REGION (OS ILIUM) 　　　

B 100-5005 7 PAIN RIGHT CALF Y 　 Y

B 100-5005 8 WEAKNESS Y 　 Y


SQL Procedure


Result Dataset (AECNT)


SAS CodePROC SORT DATA=ADAE; BY TRTAN USUBJID AESEQ; RUN;DATA AECNT(KEEP=TRTAN COL1 COLU1 SUBJCNT EVECNT); SET ADAE; BY TRTAN USUBJID AESEQ; ARRAY AEFL{3} $ TEAEFL RTEAEFL TESAEFL; ARRAY SUBJAE{3} SUBJAE1-SUBJAE3; ARRAY SCNT{3} SCNT1-SCNT3; ARRAY AECNT {3} AECNT1-AECNT3; RETAIN SCNT1-SCNT3 AECNT1-AECNT3 0; IF FIRST.TRTAN THEN DO I=1 TO hbound(SCNT); SCNT{I}=0; AECNT{I}=0;

END; IF FIRST.USUBJID THEN DO I=1 TO hbound(SUBJAE); SUBJAE{I}=0;

END; DO I=1 TO hbound(SUBJAE); IF AEFL{I}='Y' THEN SUBJAE{I}+1; END; IF LAST.USUBJID THEN DO I=1 TO hbound(SCNT); IF SUBJAE{I}>=1 THEN SCNT{I}=SCNT{I}+1; AECNT{I}=AECNT{I}+SUBJAE{I}; END; IF LAST.TRTAN THEN DO I=1 TO hbound(SCNT); COL1=I; COLU1=PUT(COL1, COL1F.); SUBJCNT=SCNT{I}; EVECNT=AECNT{I}; OUTPUT; END;RUN;

Assigns the 0 for each treatment group

Assigns the initial value (0) of each AE category for each subject

Count the number of AEs per SUBJECT for each AE category.

Count Number of subject (SCNT{i}) and Number of AEs (AECNT{i} per AE category.

Assigns the initial value (0) for the 6 variables

Output the Number of subject and Number or events for each category.


Conclusion

The RETAIN statement can carry over values from one observation to next, so it is very useful to manipulate the data across observations.


Q&A

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Effective Use of the RETAIN Statement in Programming Clinical Trial

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