Laboratory findings showed an increase in the level of inflammatory markers, which were positive for c-ANCA
. RF was positive (56.8 IU/mL) and CCP was negative (<0.5).
ANCA pattern and specificity were also noted, namely c-ANCA
, p-ANCA, PR3-ANCA and MPO-ANCA.
Characteristic Total Nonmalignancy Malignancy p value Age (median, IQR) 62 (49-72) 61 (48-72) 65 (56-73) 0.04 Male sex (%) 229 (55%) 200 (53%) 29 (71%) 0.03 eGFR (median, IQR) 23 (11-46) 24 (11-47) 19 (9-39) 0.29 C-ANCA/PR3-ANCA 237 (57%) 213 (56%) 24 (59%) 0.89 AAV, ANCA-associated vasculitis; IQR, interquartile range; eGFR, estimated glomerular filtration rate, mL-min-1.73 [m.sup.2]; C-ANCA
, cytoplasmic ANCA; PR3-ANCA, proteinase 3 ANCA.
All serology workup including anti-nuclear antibodies (ANAs), extractable nuclear antigens (ENA profile), cytoplasmic anti-neutrophil cytoplasmic antibodies (c-ANCA
), perinuclear antineutrophil cytoplasmic antibodies (p-ANCA), rheumatoid factor (RF), anti-cyclic citrullinated peptide (anti-CCP), and angiotensin converting enzyme (ACE) level came back as negative.
Perinuclear ANCA is more often positive than c-ANCA
Blood tests showed a hemoglobin concentration of 9 g/dL (reference range 14.0-17.5 g/dL), serum creatinine of 2.76 mg/dL (reference range 0.6-1.2 mg/dL), C-reactive protein of 48 mg/L (reference range 0.08-3.1 mg/L), rheumatoid factor of 742 U/mL (reference range 0-30 U/mL), and c-ANCA
(cytoplasmic antineutrophil cytoplasmic antibody) positivity (proteinase 3 autoantibody concentration, 18.3 U/mL).
Typically, this disorder is associated with a positive antineutrophil cytoplasmic antibody (c-ANCA
) but this is not always the case [2-4].
Antinuclear antibody (ANA), anti-PR3 antibody (c-ANCA
), and anti-MPO antibody (p-ANCA) were also within the normal range.
A cytoplasmic pattern (c-ANCA
) by IIF and PR-3 positivity by ELISA are suggestive of GPA.
, MPO Ab, Pr3 Ab, and ANA were negative.