THE DIAGNOSTIC-VALUE OF THE DIATOM TEST FOR DROWNING .1. UTILITY - A RETROSPECTIVE ANALYSIS OF 771 CASES OF DROWNING IN ONTARIO, CANADA

The utility and validity of the diatom test for drowning was studied u sing a retrospective analysis of 771 cases of drowning mostly from Ont ario, Canada, over the period 1977 to 1993. In this article (part one) , the utility of the test was assessed using an analysis of test outco mes. In the companion article (part two), the validity of the test was assessed by analyzing the relationship between test outcome and chara cteristics of diatoms in the bone marrow and samples of putative drown ing medium. In the present study, freshwater drownings accounted for 7 38 of the cases and 33 cases were drownings in bathtubs, pools, or toi lers. Diatoms were recovered from the femoral bone marrow of 205 cases (28%) of freshwater drowning and four cases (12%) of domestic water d rowning. There was a monthly variation in the frequency of positive te st outcomes that could not be explained by seasonal differences in the total number of drownings. However, the monthly variation was strongl y correlated with the periodic cycle of diatom blooms that occurs in f reshwater. Positive diatom tests were characterized by a limited numbe r of distinctive diatom species per case, and a restricted quantity an d size range of diatom frustules. These results indicate that the diat om test for drowning will identify approximately one in three victims of freshwater drowning and may be useful in the assessment of deaths o ccurring in bathtubs. The correlation of the outcome of the diatom tes t for drowning with diatom blooms provides further evidence for the re liability of the test.