[Preparation and application of control sera for neuromuscular disorders]

The lack of assayed quality control sera to reliably determine the presence of low creatinine, high creatinine, and high aldolase activity levels in patients with progressive muscular dystrophy prompted us to attempt the development of such sera. The mean serum creatinine and creatine values in patients with neuromuscular disorders were 0.24 mg/dl and 1.42 mg/dl, respectively. Aldolase activity spanned a wide range from normal to 273 IU/l. On the basis of these findings, sera containing 0.2 mg/dl of creatinine, 1.6 mg/dl of creatine, and 60 IU/l of aldolase activity were prepared by the reconstitution of pooled sera. The coefficients of variation (CVs) of creatinine assays for control sera containing 1.0 mg/dl or more were less than 1.5%. However, precision was poor at creatinine concentrations below 0.4 mg/dl, with CVs as high as 3.3%. Since the precision of creatinine measurement is poor at low concentrations, the creatinine assay has its own limitations if employed clinically for the purpose of evaluating renal function in patients with muscle atrophy or in children who have low serum creatinine levels. The high creatine and aldolase activity levels of the prepared control sera gave satisfactory results when analyzed for intra-assay and inter-assay variation.