Case 28: Diagnostic Testing

Case 28 Index

Take a look at some initial diagnostic testing below.
Urinalysis/microscopy, urine electrolytes
Urine sediment
Basic labs
Kidney Ultrasound

The right kidney measures 14cm in length (seen here), and the left kidney measures 15cm in length. Both are echogenic.

Basic Lab Ref

What are the highest yield tests to send next (several may be correct)?
ANCA panel
This test would be more useful in the initial work-up of a patient with nephritic syndrome – here, the clinical picture is more consistent with nephrotic syndrome. Try again!
Hepatitis B, Hepatitis C, and HIV serologies
Absolutely! The patient is hepatitis B immune (surface antibdy positive, core antibody negative). Both HIV and hepatitis C antibodies are negative. Hepatitis B is associated with membranous nephropathy (MN) and HIV can lead to collapsing FSGS (both nephrotic syndromes). Though Hepatitis C is more often associated with membranoproliferative glomerulonephritis, hepatitis C-associated MN is also possible.
Erythrocyte sedimentation rate (ESR), C-reactive protein (CRP)
While these may be useful to assess his level of inflammation, ESR and CRP are non-specific and will not be highest yield in sorting out his kidney problem. Try again!
Anti-glomerular basement membrane (GBM) antibody level
Not the best test for this patient with nephrotic range proteinuria without hematuria. Try again!
Serum protein electrophoresis (SPEP) and free light chains (FLC)
Great choice! SPEP shows a polyclonal gammopathy with IgG 1700, IgA 600, IgM 15. The ratio of kappa to lambda FLC is within normal limits.
Antinuclear Antibody (ANA)
Good choice! This patient’s ANA is 1:80 (normal <1:80). For good measure you also send an anti-dsDNA, which is negative.
Hemoglobin A1C
You should absolutely check for diabetes in a patient with proteinuria and enlarged kidneys. His A1c is 5.9%, consistent with pre-diabetes.
Anti-PLA2R Antibody
This is a reasonable test to send for a with nephrotic range proteinuria. You’ve sent the sample to an outside laboratory, and it will take a few days to come bac.

The tests above should help narrow down our differential diagnosis, but we need a biopsy to get to our final answer. Click here to perform the kidney biopsy!

Case 28 Index
Case 28 Introduction
Case 28 Physical Exam