Immunonephelometric quantification of free haemoglobin.

A fully mechanized immunonephelometric method for rapid and specific determination of free haemoglobin in serum, plasma, or aqueous haemolysates is described. It utilizes commercially available rabbit antiserum against human haemoglobin and the Behring Nephelometer Analyser. A single determination is performed within 6 minutes and requires 250 microliters total sample volume. The measuring range is about 9-2300 mg/ml haemoglobin. Precision is characterized by intraassay coefficients of variation of 3.4% and 1.6%, and interassay coefficients of variation of 8.2% and 5.6% for haemoglobin concentrations of 29 mg/l and 119 mg/l, respectively. Accuracy of the method is shown by close correlation to haemoglobin determination by cyanohaemiglobin spectrometry (r = 0.9837). Interference may occur for visibly lipaemic samples. A preliminary comparison of different specimens drawn in parallel shows lowest haemoglobin concentrations in citrate plasma, followed by heparin plasma and by serum, while EDTA-plasma is unsuitable for this analysis.