IPDE - Extranet Systems - World Health Organization

82 A. W. Loranger
summarizes them for one popular instrument, the Schedule for Affective
Disorders and Schizophrenia-Lifetime version (SADS-L). The findings
indicate moderate, but at times disappointing, stabilities that are not consistently
superior to many of those obtained in this study with the PDs. It
should be noted, however, that four of the five studies involved longer
time intervals than six months. The one study within that timeframe
reported a kappa of 0.63 for the presence or absence of any SADS-L
diagnosis. This compares with 0.62 in DSM-III-R and 0.59 in ICD-10
for the presence or absence of any specific PD on the IPDE. The studies
in Table 1 did not repon an overall weighted kappa, thus precluding
comparisons based on that statistic. Another potentially relevant difference
is that in most of these studies, the initial and repeat interviews were
conducted by different interviewers. One study,s however, did not find
significant differences in stability when the same and different interviewers
were used, another study6repmed an inconsistent effect.
There is very little literature on the temporal stability of criteria-based
PDs diagnosed with semistructured interviews. There appear to be only
three studies that involved more than a brief test-retest interval. One was
based on an early trial version of the PDE? which is no longer extant.
The other twolO.'l reported on the stability of the Structured Interview for
DSM-111 Personality Disorders (SIDP). Pfohl et repeated the SIDP
in 36 depressed inpatients after 6 to 12 months. The kappa values, which
ranged from 0.16 to 0.84, are problematic because of the small sample
sizes of the individual disorders. Similar findings were obtained by van
den Brink in the Netherlands."
The belief that interviewers are perfectly interchangeable would seem
naive in view of the potential influence that the age, sex, and personality
of an inte~ewer might have on the information provided by a subject.
The assumption made by those who use semistructured interviews is that
such factors ordinarily are not a major source of error. In planning the
present study, consideration was given to a design in which half of the
interviews would be repeated by the same examiner and half by a different
examiner. This would have helped to determine how much the interviewers
themselves, in addition to their rating decisions, contributed to
the instability of the measures. However. concerns about scheduling and
the availability of interviewers influenced the decision to use the same
interviewers whenever possible. As a result, 93% of the interviews were
given by the same examiner on both occasions.
A second interview, whether conducted by the same or a different
person, may be contaminated by the experience of the first interview.