Development of an enzymatic assay for sphingomyelin with rapid and automatable performances: Analysis in healthy subjects and coronary heart disease patients.

Sphingomyelin (SM) is an important choline group-containing phospholipid and is considered to be an independent risk factor for coronary heart disease. We have developed a specific enzymatic assay for SM measurement with rapid and automatable performances by using two-reagent system involving sphingomyelinase. We performed within-run and between-run precision, linearity test, detection limit, recovery test and interference to validate this assay. Then, we measured the serum SM concentration in 194 healthy subjects and 141 consecutive patients undergoing coronary angiography. The within-run and between-run coefficients of variation for SM concentrations were 1.1-1.3% and 1.0-1.2%, respectively. Quantitative measurements to a lower limit of 30 μmol/L were shown to be possible. The recoveries of the exogenously added SM to the control samples were 98.7%-101.5%. No effect was observed after the addition of some interference materials. The mean ± SD of the serum SM concentration in the 194 healthy subjects was 553.3 ± 100.1 μmol/L. We found that the SM concentration was significantly higher among an acute coronary syndrome subjects than among the healthy subjects (P<0.01) and that the serum SM concentrations were significantly correlated with the serum magnesium concentration. We have developed a rapid and automatable enzymatic assay for SM that enables the automatic measurement of choline-containing phospholipids. This assay may be useful for various types of biochemical and clinical research.