Construct validity of life chart functioning scales for use in naturalistic studies of bipolar disorder

This study examined the construct validity of the functional impairment scales of the National Institute of Mental Health (NIMH) prospective life-charting methodology (LCM-p(TM)). Twelve male and 28 female bipolar participants were recruited from the community through advertisements. Diagnoses of bipolar I or II were confirmed using Structured Clinical Interview for DSM-IV Axis I Disorders (SCID-I). Patients completed life charts for three consecutive months. At the end of each month, a trained clinician administered the Hamilton Depression Rating Scale (HDRS) and the Young Mania Rating Scale YMRS by telephone, followed by ratings using the Global Asessment of Functioning (GAF), and Clinical Global Impression (CGI) for bipolar disorder. Data was analyzed separately for each month (time 1, time 2, and time 3). Complete data was available for 35 participants at time 1, 36 at time 2 and 32 at time 3. Spearman correlations demonstrated significant convergent validity at times 2 and 3 for life chart measures of mania (HIGH) and CGI-mania, and at all three times for life chart depression (LOW) and CGI-depression, with corresponding discriminant validities. The GAF was positively correlated with HIGH and negatively correlated with LOW at time 2 and 3 only. HAM-D and LOW also showed convergent and discriminant validity for all three times. For HIGH and YMRS, however, there was a strong significant correlation at time 3 only. While the use of heterogeneous methods maximizes differences between measures, it also appears that bipolar patients are less consistent in reporting functional impairment due to mania than due to depression. The construct of life chart dysfunction due to mania does not consistently measure the same construct as similar clinician ratings of mania. Life chart dysfunction due to depression shows higher construct validity.