Although growing interest exists in the bipolar spectrum, fully structured diagnostic interviews might not accurately assess bipolar spectrum disorders. A validity study was carried out for diagnoses of threshold and sub-threshold bipolar disorders (BPD) based on the WHO Composite International Diagnostic Interview (CIDI) in the National Comorbidity Survey Replication (NCS-R). CIDI BPD screening scales were also evaluated.
The NCS-R is a nationally representative US household population survey (n = 9282 using CIDI to assess DSM-IV disorders. CIDI diagnoses were evaluated in blinded clinical reappraisal interviews using the non-patient version of the Structured Clinical Interview for DSM-IV (SCID).
Excellent CIDI-SCID concordance was found for lifetime BP-I (AUC = .99 κ = .88, PPV = .79, NPV = 1.0), either BP-II or sub-threshold BPD (AUC = .96, κ = .88, PPV = .85, NPV = .99), and overall bipolar spectrum disorders (i.e., BP-I/II or sub-threshold BPD; AUC = .99, κ = .94, PPV = .88, NPV = 1.0). Concordance was lower for BP-II (AUC = .83, κ = .50, PPV = .41, NPV = .99) and sub-threshold BPD (AUC = .73, κ = .51, PPV = .58, NPV = .99). The CIDI was unbiased compared to the SCID, yielding a lifetime bipolar spectrum disorders prevalence estimate of 4.4%. Brief CIDI-based screening scales detected 67–96% of true cases with positive predictive value of 31–52%.
CIDI prevalence estimates are still probably conservative, though, but might be improved with future CIDI revisions based on new methodological studies with a clinical assessment more sensitive than the SCID to sub-threshold BPD.
Bipolar spectrum disorders are much more prevalent that previously realized. The CIDI is capable of generating conservative diagnoses of both threshold and sub-threshold BPD. Short CIDI-based scales are useful screens for BPD.