What is the role of urinalysis in the workup of light chain nephropathy?
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What is the role of urinalysis in the workup of light chain nephropathy?
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@nowelle Urinalysis results may indicate low-grade proteinuria. A discrepancy between the results of a urine dipstick test for protein and the findings from a test for 24-hour urine protein excretion should suggest the possibility of light-chain proteinuria. Light-chain proteins in the urine cannot be detected using Albustix or other dipstick methods.
Perform the Putnam heat test or the sulfosalicylic acid (SSA) test (with Exton reagent) to help detect urinary light-chain proteins. The results from either test are insensitive. The Putnam heat test can help detect urinary light chains only when the concentration exceeds 150 mg/dL. False-negative results are common with the SSA test if the specific gravity of urine is less than 1.01.
If a patient has a negative result from the Albustix test (which detects albumin) and a positive result from the SSA test, consider the possibility of light-chain proteinuria.