The SRPHK1 outcome measure for cocaine-dependence trials combines self-report, urine benzoylecgonine levels, and the concordance between the two to determine a cocaine-use status for each study day.
BACKGROUND
There is currently no FDA-approved medication for cocaine dependence and no standard primary outcome measure for reduction of cocaine use in cocaine-dependence trials. The ability to detect a significant medication effect will depend, in part, on the primary outcome measure utilized. The goal of the present paper is to compare self-report or either of two urine toxicology measures used alone to a relatively new measure -- the SRPHK1 -- which combines self-report, quantitative urine benzoylecgonine levels, and an estimate of the concordance between the two to determine the cocaine-use status of each study day.


METHODS
Datasets from two separate randomized, placebo-controlled cocaine-dependence trials were used to compare four cocaine-use outcome measures.


RESULTS
The two data sets yielded very similar findings and suggest that the combined measure is associated with significantly fewer missing data than urine toxicology and that estimated cocaine use varied significantly depending on which measure was used, with the lowest use estimate being yielded by self-report, the highest by the two urine toxicology measures evaluated, and an intermediate value obtained using the combined measure. The results also suggest that the concordance between self-report and urine toxicology is around 90% at the beginning of the clinical trial but decreases to around 75% by the end of the trial.


CONCLUSIONS
By combining the objectivity of urine toxicology with the reduced incidence of missing data characteristic of self-report, the SRPHK1 may provide advantages over self-report or urine toxicology measures used alone. In any case, the SRPHK1 provides an interesting complement to these other outcome measures and may warrant further evaluation.
Somoza
Eugene
E
Department of Psychiatry, University of Cincinnati College of Medicine, Cincinnati, OH 45267, USA. somoza@uc.edu
Somoza
Peggy
P
Lewis
Daniel
D
Li
Shou-Hua
SH
Winhusen
Theresa
T
Chiang
Nora
N
Vocci
Frank
F
Horn
Paul
P
Elkashef
Ahmed
A
D000328:Adult; D003042:Cocaine / Q000031:analogs & derivatives* / Q000652:urine; D019970:Cocaine-Related Disorders / Q000235:genetics* / Q000652:urine*; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D017346:Protein Serine-Threonine Kinases / Q000235:genetics*; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires; D013997:Time Factors
C005618:benzoylecgonine; C087728:SRPK1 protein, human; D017346:Protein Serine-Threonine Kinases; D003042:Cocaine