A number of conditions may be associated with proteinuria that is not detected by the urine dipstick test for protein.
Proteins poorly detected by the dipstick method:
(1) immunoglobulins
(2) Bence Jones proteins
(3) hemoglobin
(4) mucoprotein
Conditions masking the level of proteinuria:
(1) dilution (as indicated by a low specific gravity)
(2) pregnancy
If a specimen is diluted, then repeat testing should be done on a less dilute specimen.
If proteinuria is expected clinically but negative on dipstick testing, then consider:
(1) urine protein testing using sulfosalicylic acid
(2) a test for Bence Jones proteins
(3) urine protein electrophoresis and urine immunofixation
Diabetics may secrete an increased amount of albumin that is below the detection limit of a dipstick (microalbuminuria, indicating a micro amount of albuminuria rather than a small form of albumin). This can be measured using a microalbuminuria method.
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