Gempp E, Morin J, Louge P, Blatteau JE. Reliability of plasma D-dimers for predicting severe neurological decompression sickness in scuba divers. Aviat Space Environ Med 2012; 83:771–5. Background: A low-grade process of coagulation activation in association with severe neurological decompression sickness (DCS) in divers has been anecdotally observed. We aimed to investigate whether measurement of plasma D-dimers and other hemostatic parameters in injured scuba divers were effective as prognostic biomarkers of neurological DCS, and we compared the diagnostic accuracy of a combination of D-dimers test and initial clinical assessment with either one alone. Methods: Eligible for the study were 84 recreational divers (69 men, 46 ± 10 yr; 15 women, 44 ± 8 yr) referred for neurological DCS in 2007-2011 and treated with hyperbaric oxygen. Blood tests were collected for D-dimers, fibrinogen, and platelet count with a time interval less than 8 h upon admission. Presentation severity was rated numerically for the acute event with a validated scoring system and clinical outcome was assessed by a follow-up examination at 3 mo. Indices of accuracy for D-dimers test, initial clinical score, and combination were estimated. Results: Incomplete recovery was reported in 26% of patients with a definite relationship between elevated D-dimers and presence of sequelae after multivariate analysis. We did not find differences for other blood coagulation variables between outcome groups. Combination of positive D-dimers (cut-off value of 0.40 μg · ml⁻¹) with severe initial presentation attained a higher diagnostic accuracy than either method alone (post-test probabilities = 100%, 86%, and 57%, respectively). Conclusion: This study suggests that determination of plasma D-dimers, a marker of activation coagulation, improve the prognostication of neurological DCS affecting scuba divers when combined with presenting severity score.