Negative, but a good thought! ANCA-associated vasculitis typically presents as a rapid progressively glomerulonephritis (RPGN), and while it typically affects individuals older than 50 years old, it can present with a nephritic syndrome at any age.

C3 6 mg/dL (ref: 90 – 180 mg/dL); C4 8 mg/dL (ref: 10 – 40 mg/dL). Great choice, we should look for complement-mediated diseases in patients like this with a nephritic picture.

This test is low yield here. Our patient is presenting with a nephritis, and anti-PLA2R is more helpful to narrow our differential of nephrotic syndrome.

1:1080 (reference <1:80). Yikes! This patient has a significantly elevated ANA titer, which can help us narrow our differential further.

<5 IU/mL (reference <14IU/mL). It is not unreasonable to send this test in search of a cryoglobulinemic glomerulonephritis, though it may be less likely in this case.

You’ve clearly picked up on this patient’s cytopenias (low cell counts). However, a bone marrow biopsy is an invasive test and might not give us the diagnosis. For now, our colleagues in hematology advise other diagnostic tests to help this patient.

Negative, but a reasonable test to have sent in this young patient presenting with evidence of nephritis, particularly given her recent febrile illness.