Improving the efficiency of screening for major depression in people with spinal cord injury.
OBJECTIVE
To investigate the metric properties, relative efficiency, sensitivity and specificity, and positive predictive value of a short form of the Patient Health Questionnaire-9 (PHQ-9) that may be used as a screening test for depression.


METHODS
Data from the National Spinal Cord Injury Statistical Center Database containing 3,652 records with complete data for the PHQ-9 were analyzed using Confirmatory Factor Analysis, Item Response Theory Graded Response Model analysis, and sensitivity and specificity analysis of classification.


RESULTS
A scale comprised of items 1, 2, and 6 from the PHQ-9 has a relative efficiency of 0.66 compared to the 9-item scale. Using this 3-item scale and a cutoff score of 3 or more provides specificity of 0.93 and sensitivity of 0.87; a cutoff of 4 provides specificity of 0.95 and sensitivity of 0.82. The shorter version of the scale reduces the effect of response bias caused by gender. The relative efficiency of the 9-item scale is 0.88 for women compared to men; the 3-item scale increases the relative efficiency to 0.93.


CONCLUSIONS
A 3-item scale provides adequate information for clinical screening purposes. Cutoff scores of either 3 or 4 are acceptable and present options for decision making within a particular clinical setting. Additionally, the 3-item scale reduces the effect of gender of the respondent on the score obtained.
Graves
Daniel E
DE
Department of Physical Medicine and Rehabilitation, Baylor College of Medicine, Houston, Texas, 77030, USA. dgraves@bcm.tmc.edu
Bombardier
Charles H
CH
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D015897:Comorbidity; D003865:Major Depressive Disorder / Q000175:diagnosis* / Q000453:epidemiology*; D005260:Female; D006304:Health Status; D006801:Humans; D008297:Male; D008403:Mass Screening / Q000379:methods*; D008875:Middle Aged; D011237:Predictive Value of Tests; D015995:Prevalence; D015203:Reproducibility of Results; D013119:Spinal Cord Injuries / Q000453:epidemiology* / Q000523:psychology*; D011795:Surveys and Questionnaires / Q000592:standards*