ABSTRACT
Basic rules establish that the total serum complement determination (CH50) should be done after quick serum separation at 4 degrees Celsius. When there is a long period between blood sample collection and laboratory tests, the results may not be exact, with findings being below normal level due to thermolability and dysfunction of some of the components. Sera from 15 normal individuals and 15 patients with Systemic Erithematous Lupus (SEL) were studied. CH50 determinations were performed by the radial immunohemolysis technique according to the above basic rules and compared to determinations performed after 4, 8, 12 and 24 h in sera maintained at room temperature and after 24 h in those maintained at 4 degrees Celsius. Five samples (2 controls and 3 lupoid) were stored at -2O degrees Celsius and -7O degrees Celsius. CH50 determinations were performed weekly in sera kept at -2O degrees Celsius and after l month in those stored at -7O degrees Celsius. Analysis of the results suggest that, if blood samples are kept at room temperature and the determination is performed within about 8 h, the results are still reliable, that is, they will be within normal levels. The same will happen if the sera are stored at -2O degrees Celsius or -7O degrees Celsius for up to l month.