OBJECTIVETo investigate the value of serum cystatin C (Cys-C), urinary Cys-C, urinary retinol binding protein (RBP) and urinary neutrophil gelatinase-associated lipocalin (NGAL) in the early assessment of multiple myeloma (MM) and their characteristic changes in different pathological types of renal impairment.

METHODSAccording to glomerular filtration rate (eGFR), the patients were divided into two groups, of which marked group A with normal renal function, the other marked group B with abnormal renal function. Sixty healthy subjects were chosen as control. Detection of the serum Cys-C, urinary RBP, urinary Cys-C, urinary NGAL, serum creatinine (Scr), urinary microalbumin (MAU) and urinary α1-microglobulin (α1-MG) were performed. Renal biopsy was carried out for patients who had abnormal serum Cys-C, urinary Cys-C, urinary RBP, urinary NGAL and were willing to accept further test.

RESULTSCompared with healthy controls, the serum Cys-C, urinary RBP, urinary Cys-C, urinary NGAL of group A were significantly higher than that of healthy controls. Six group A patients received renal biopsy, and varying degrees of renal damage were discovered. The serum Cys-C, urinary RBP, urinary Cys-C and urinary NGAL positive rate were 66.7%, 66.7%, 66.7% and 83.3%, respectively. Of twenty-four cases received biopsy after abnormal examination results were shown, six turned out to be amyloidosis, twelve cast nephropathy (CN) and 6 monoclonal immunoglobulin deposition disease (MIDD). Compared with MIDD and amyloidosis, the urinary Cys-C and NGAL of the CN group are significantly higher (P < 0.05). Compared with CN and amyloidosis, urinary RBP of MIDD is significantly higher (P = 0.043). Compared with MIDD and CN, the MAU of amyloidosis is significantly higher (P = 0.006).

CONCLUSIONCompared with the conventional indicators, serum Cys-C, urinary Cys-C, RBP and NGAL are more sensitive in early assessment of MM patients with renal damage. The MAU is higher in amyloid, the urinary Cys-C and urinary NGAL are significantly elevated in CN, the urinary RBP is significantly elevated in MIDD.