[Creatinine index in the diagnosis of myopathies. New method for determination].

A new spectrophotometric method for determination of creatine and creatinine values, and hence calculation of the creatine index, is reported. Micropipetting of fingerprick quantities (0.3 ml) of blood enables values to be obtained from obese and progressive muscular dystrophy subjects, whose veins are difficult to find without damaging the tissues.