Volume 38, Issue 4 (July 1993)
Cholinesterase Activity in Postmortem Blood as a Screening Test for Organophosphate/Chemical Weapon Exposure
This study was undertaken to determine whether postmortem blood cholinesterase activity could be used as a screening test for exposure to nerve agents. Whole blood cholinesterase activity at 25°C was analyzed for a one week period in order to simulate the battle field collection problems of: hemolyzed blood samples, delayed recovery of the specimen, and unrefrigerated transfer to the testing facility. A total of 53 nonpreserved postmortem whole blood specimens were analyzed in triplicate for cholinesterase activity by the Δ pH method of Michel. There was a negligible loss of cholinesterase activity by the seventh day of the study. The enzyme activities of the specimens had a mean value (range) of 0.48 (0.20 to 0.74) initially and 0.45 (0.07 to 0.70) pH units after one week. Whole blood from five healthy adults remained essentially unchanged during this period, with an initial value 0.59 (0.52 to 0.67) and a final value of 0.52 (0.46 to 0.62) pH units. To compare postmortem and simulated nerve agent values, aliquots from 18 of the original 53 postmortem specimens were frozen during day one of the study, thawed on day seven and a cholinesterase inhibitor added. These specimens were then analyzed with the other specimens. All values from inhibited specimens were essentially zero (0.0 to 0.01) pH units compared to a range of 0.07 to 0.61 pH units for matched, uninhibited, day seven postmortem specimens. Fifteen actual nonpreserved specimens from the battlefield were analyzed as verification of screen performance. Their results fell within the uninhibited postmortem range above. All of the 53 day one postmortem, day seven postmortem, and 13 of 15 battlefield specimen cholinesterase activities were significantly greater than the levels found in the 18 specimens exposed to the cholinesterase inhibitor. We conclude that the cholinesterase activity in postmortem specimens collected within a one week period of death can be used as a screen for possible nerve agent exposure.