Computer assisted diagnosis of malformation syndromes: an evaluation of three databases (LDDB, POSSUM, and SYNDROC)

Computer programs which can be used as an aid to diagnose multiple congenital anomaly syndromes have been used for many years, but up to now they have been evaluated very rarely. The diagnostic abilities of three of these systems [LDDB (London Dysmorphology Database), POSSUM (Pictures of Standard Syndromes and Undiagnosed Malformations), and SYNDROC] were analyzed. All three programs are based on an algorithm which defines a diagnosis by a set of phenotypic components all having the same weight (descriptive algorithm). A second algorithm is applied by SYNDROC to rank competing diagnoses in order of probability. This pseudo-Bayesian algorithm provides a coefficient of certitude (CC). For a test the clinical findings of 102 patients who had received a firm diagnosis were used. Two search strategies were tried: "novice's strategy" with all findings taken for a search and "expert's strategy" with a selected set of anomalies. Only those diagnoses that were suggested with the 1st rank, defined as the highest degree of agreement, or the highest CC were studied. The greatest resemblance between suggestions of the databases and the clinical diagnosis was obtained with the expert strategy. The highest number of matches were produced by SYNDROC (80 with expert strategy) and the lowest by POSSUM (54 with novice strategy). The overall agreement between the databases is about 40% for the 1st rank. This number reflects that different authors use different pivotal signs for the description of a syndrome. With the pseudo-Bayesian algorithm 59 cases obtained the highest CC value. Great difficulties exist with the subjective estimates for the calculation of these values; the absolute CC values seem to be meaningless. A small number of unusual cases with special combinations of anomalies provide serious problems for correct diagnosis.