Renal plasma clearance: a valuable marker in myelomatosis.

Forty-two consecutive patients with untreated myelomatosis (MM) formed the basis of settling the validity of measuring the renal plasma clearance (RPC), either indirectly using the serum creatinine or directly using the glomerular filtration rate (GFR) when studying anaemia, calcium metabolism, proteins in serum and urine, and prognosis. Patients without light chain excretion in the urine had a higher GFR (P less than 0.01) than patients with light chain excretion. The haemoglobin concentration (Hb) was strongly correlated (P less than 0.001) to both, serum creatinine and GFR. Patients with normal serum concentrations of the physiological immunoglobulins had higher Hb (P less than 0.01) than patients with reduced serum immunoglobulins. Patients with serum calcium greater than 3.00 mmol/1 had additional reduced GFR compared with the other myeloma patients. The serum parathyroid hormone was decreased (P less than 0.01) and inversely correlated to the GFR. Patients with increased serum creatinine, reduced GFR or with osteolytic bone lesions had a decreased survival rate. The study shows that the major factor in prediction of Hb and prognosis in patients with MM is the RPC expressed either as the serum creatinine or the GFR. In addition, the significant correlations between the GFR and the other variables in MM assessed the RPC to be a useful and valuable marker in studies of anaemia, protein and calcium metabolism and prognosis in MM.