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17 INNOSC Theranostics and Pharmacological Sciences, 2022, Vol. 5, No. 2 Govender and Hodkinson
3. Results granulomatosis with GPA, and nine had renal-
limited vasculitis (RLV) with pauci-immune
Of 945 ANCA tests performed, 790 clinical records necrotizing GN on renal biopsy and no extra-renal
were identified and reviewed, while 155 patient manifestations. Only five of the RLV patients were
records were missing (Figure 1). Among the ANCA-positive (mostly MPO-positive).
patients, 62 had undergone multiple tests, resulting Of all ANCA tests performed, 31 patients (3.9%)
in a total of 133 duplicate tests. Most tests were had tested positive for ANCA, of which 5 were
ordered for inpatients (63.0%). Overall, only true positives and 26 were false positives showing
193 patients (24.4%) had indications that met the no evidence of AAV. Of these false positives,
1999 guidelines for ANCA testing. The remaining
597 (75.6%) did not meet the guidelines criteria. 11 (42.3%) were associated with chronic infections,
The departments that requested the most ANCA such as human immunodeficiency virus (HIV), TB,
tests were Medicine, Ophthalmology, Neurology, and syphilis, while three (11.5%) had autoimmune
and Surgery. Notably, surgery had 98.9% of its tests diseases (Table 4). There was no explanation for
ordered for non-guideline indications (Table 2). the positive results in 13 patients (50%). In terms
The most common clinical problems for which of drug-induced ANCA positivity, no commonly
ANCA tests were ordered outside of guideline associated drugs, including anti-thyroid drugs, D
indications included critical limb ischemia (9.6%), penicillamine, sulfasalazine, allopurinol, cocaine,
stroke (7.3%), uveitis (5.7%), acute kidney injury or TNF inhibitors, were implicated in the false-
(4.9%), and interstitial lung disease (4.4%). On the positive ANCA group. The sensitivity, specificity,
other hand, the most common guideline indications PPV, and NPV for the total cohort were 50.0%,
were glomerulonephritis (GN) (52.1%), peripheral 96.7%, 16.1%, and 99.3%, respectively.
neuropathy (19.0%), scleritis (10.5%), and Of the 193 ANCA tests which met guideline
cutaneous vasculitis (9.0%). indications for testing, 14 patients tested positive
Ten patients (1.3%) were diagnosed with for ANCA, of which five were true positive, while
AAV over the 12 months, and these patients were the remaining nine were false positives, showing
predominantly female, of mixed racial ancestry, no evidence of AAV. When focusing only on
with a mean (SD) age of 54.5 (16.4) years (Table 3). patients who met the guideline indications for
One patient was diagnosed with ANCA-negative testing, the PPV improved, although it remained

Figure 1. Flow diagram of anti-neutrophil cytoplasmic antibody tests performed over 12 months at a tertiary
hospital in South Africa.

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