RAPID QUANTITATIVE-EVALUATION OF PLASMA D-DIMER LEVELS IN THROMBOTIC STATES USING AN AUTOMATED LATEX PHOTOMETRIC IMMUNOASSAY

To evaluate a recently developed latex photometric immunoassay (LPIA) that which can measure 40 samples quantitatively within 30 minutes, we measured D-dimer levels in blood samples obtained from patients with disseminated intravascular coagulation (DIC). Linearity of D-dimer determination was shown over the range from 0.5 to 36-mu-g/ml, and recovery studies demonstrated 94 to 108 % recovery. The intra-assay and inter-assay co-efficients of variation ranged from 0.6 to 11.3 % at plasma D-dimer levels of 0.54 to 30.1-mu-g/ml. No interference by lipids, bilirubin, haemoglobin, rheumatoid factor, or gamma-globulin was noted. The normal D-dimer range was < 0.5-mu-g/ml in healthy ambulatory subjects, while the level in elderly subjects with atherosclerosis (14 %) or in immobilized subjects (38 %) was well above this limit. There was a strong correlation between plasma and serum D-dimer levels (r = 0.993). D-dimer levels measured by this LPIA showed a good correlation with those determined using two kinds of ELISA. The LPIA D-dimer levels were elevated in some subjects with diseases predisposing to DIC, but remained below 10.0-mu-g/ml. On the other hand, the LPIA D-dimer levels in DIC subjects were almost always above 10.0-mu-g/ml. Our study showed that a hypercoagulable state should be suspected when the LPIA D-dimer level is > 0.5-mu-g/ml and that DIC should be diagnosed when the level is > 10.0-mu-g/ml in the presence of an appropriate underlying disease. This LPIA system can rapidly evaluate the presence of a hypercoagulable state as accurately as any ELISA, and thus seems potentially valuable for both emergency and routine laboratory use.