title: [Diagnostic validity of Zung's self-rating depression scale on primary care patients].
abstract: BACKGROUND
  Although the Spanish version of the Zung's Self-Rating Depression Scale (SDS) is widely used, there are no studies about its validity as a diagnostic test in primary health care patients.
  
  
  METHODS
  In a first phase, a sample of 350 consecutive primary care patients was assessed with the SDS. In a second phase, a subsample composed by all the positive test results and 1/3 of the negatives selected at random, was assessed with the modules of current Major Depressive Episode and Dysthymia of the Structured Clinical Interview for DSM-IV. Specific methods to avoid verification bias were used. Prevalence, sensitivity and specificity, predictive values, Receiver Operating Characteristic (ROC) curve, and Stratum Specific Likelihood Ratios (SSLR) were calculated.
  
  
  RESULTS
  Prevalence estimations of major depression and dysthymia were 14,7% (IC95%: 10,7-18,7%) and 4,6% (IC95%: 2,4%-6,8%) respectively. Sensitivity and specificity to detect both diagnoses were 0,95 (IC95%: 0.87-1) and 0,74 (IC95%: 0,68-0,79). Area under ROC curve was 0,93. SSLR for scoring < 50 led to a post-test probability of 0.01. In the stratum with scoring > 69 the SSLR generated a post-test probability of 0.96. Less conclusive results were obtained by intermediate strata.
  
  
  CONCLUSIONS
  The SDS is effective in primary care patients and shows operating characteristics comparable to other depression assessment scales. SSLR provides practical information to estimate the probability of suffer a depressive disorder in individual patients.
authors.affiliation: Centro de Atención Primaria de Constantí, Instituto Catalán de la Salud, Spain. earagones@ptarragona.scs.es
authors.forename: E
authors.initials: E
authors.lastname: Aragonès Benaiges
authors.forename: R M
authors.initials: RM
authors.lastname: Masdèu Montalà
authors.forename: G
authors.initials: G
authors.lastname: Cando Guasch
authors.forename: G
authors.initials: G
authors.lastname: Coll Borràs
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D003863:Depression / Q000175:diagnosis*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011320:Primary Health Care; D011569:Psychiatric Status Rating Scales; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
vernacular_title: Validez diagnóstica de la Self-Rating Depression Scale de Zung en pacientes de atención primaria.