Reliability of Best-Estimate Diagnosis in Genetic Linkage Studies of
Major Psychoses: Results from the Quebec Pedigree Studies.
M. Maziade, M.A. Roy, J.P. Fournier, D. Cliche, C. Merette,
C. Caron, Y. Garneau, M. Montgrain, C. Shriqui, C. Dion, et. al.
American Journal of Psychiatry , 149(12), 1674--1686 (1992 Dec)
Abstract
OBJECTIVE: Diagnostic classification and reliability are critical in
genetic linkage studies of schizophrenia and bipolar disorder. To
establish an optimal diagnostic procedure, the authors drew 13
methodological elements from 38 major linkage studies and workshop
reports. They determined reliability for a consensus best-estimate
diagnostic method based on these 13 features. METHOD: Each of 59
subjects from several large multiplex pedigrees, densely affected by
either schizophrenia or bipolar disorder, received a best-estimate
diagnosis from unblind diagnosticians in the field and also from a
panel of four research psychiatrists who were blind to the proband's
and relatives' clinical status. The best estimate was based on
personal diagnostic interviews, all available medical records, and
family history data. RESULTS: The diagnostic concordance between the
field team and the blind psychiatric board yielded 78% to 90%
agreement for the whole sample (kappa = 0.83-0.88) and 71% to 87%
agreement for the subjects given field diagnoses (kappa =
0.76-0.83). The diagnoses made by the unblind field diagnosticians
were biased toward a greater severity (or certainty) level in the
diagnostic hierarchy (schizophrenic or bipolar) and more consistency
with the most prevalent diagnosis affecting the pedigree.
CONCLUSION: Since several previous linkage studies used diagnoses
made by diagnosticians who were not blind to the status of the
probands and the relatives or did not use a consensus best-estimate
diagnosis, further reliability studies of different aspects of the
best-estimate method and of its effect on linkage studies are
needed. Such research is imperative given the serious impact of
diagnostic misclassifications on genetic linkage results.
