Investigations
1st investigations to order
fasting qualitative serum cryoglobulins
Test
To avoid false-positive results due to cryofibrinogenaemia or heparin-precipitable products, blood samples without anticoagulation should be examined. If samples containing anticoagulants are used, fibrinogen in plasma will convert to fibrin, which may have cryoprecipitable properties. Thus, serum instead of plasma should be used. Fasting samples are preferred, to minimise turbidity.[4][41]
Cryoglobulins may not be initially detected. Repeat testing under more vigorous conditions should be considered.
Result
presence of cryoglobulins
FBC
Test
Included as part of the evaluation for organ (e.g., bone marrow, liver) involvement.
Result
may be normal
comprehensive blood chemistry profile
Test
To evaluate renal and hepatic function. Elevation of transaminases may suggest the presence of hepatitis. Renal dysfunction should alert the clinician to a possible underlying glomerulonephritis.
Result
may be high
erythrocyte sedimentation rate, CRP
Test
Included as part of initial workup. Acute phase reactants are typically elevated.[6]
Result
may be high
urinalysis
Test
Suggestive of renal involvement.[4]
Result
may show active urinary sediment, haematuria, proteinuria
ECG
Test
Baseline testing in a patient with significant illness.[4]
Result
may show ischaemia
CXR
Test
Indicated if respiratory involvement is suspected.
Result
may show infiltrates
rheumatoid factor
Test
IgM has rheumatoid factor activity.
Result
may be positive
complement CH50, C3, C4
Test
Marked depression of early components of complement C1q and complement 4 (C4) may be seen, but complement 3 (C3) remains relatively normal and may fluctuate with disease activity. CH50 levels are also reduced.
In patients with hepatitis C virus-related cryoglobulinaemia treated with interferon, erythrocyte sedimentation rate, C4, and CH50 levels remain within normal range.[1][4][26]
Result
may be low
hepatitis C virus (HCV) antibody
Test
HCV infection is strongly associated with mixed cryoglobulinaemia. Positive viral serologies indicate active infection.[4]
Result
may be positive
hepatitis B virus antibody
Test
Positive viral serologies indicate active infection.[4]
Result
may be positive
Investigations to consider
HIV antibody
Test
Positive viral serologies indicate active infection.[4]
Result
may be positive
antinuclear antibody (ANA), Sjogren's syndrome antigens, extractable nuclear antigen (ENA) antibody
skin biopsy
Test
A skin biopsy of a relatively fresh lesion should be performed in adult patients with suspected leukocytoclastic vasculitis. This is the hallmark of mixed cryoglobulinaemia.
Result
leukocytoclastic vasculitis
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