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20 INNOSC Theranostics and Pharmacological Sciences, 2022, Vol. 5, No. 2 Govender and Hodkinson
beneficial, reducing false-positive rates by up to of tissue diagnosis as the gold standard when
27.0% and increasing ANCA positivity by 11.8% small vessel vasculitis is highly suspected [19].

without missing AAV cases [3,11]. The ANCA-negative group exhibits poorer renal
False-positive ANCA tests have been well- outcomes and less extrarenal involvement.
described, and in the present study, they resulted Limitations of this study include the imprecision
in a lower PPV than what has been described of retrospective record review where clinician
elsewhere [10,12-14]. In our study, among the notes may have inadequately documented the test
26 patients who tested positive for ANCA but indication, together with a large number of missing
showed no evidence of AAV, chronic infection records. In addition, this audit was conducted in a
was noted in 42.3% of the cases. Elsewhere, tertiary hospital, and the results are not generalizable
chronic infections, including TB, malaria, leprosy, to other health-care platforms.
suppurative lung disease, infective endocarditis,
hepatitis B and C, and HIV, have been noted to 5. Conclusions
cause positive ANCA results [5,15]. In the pre- Our study shows indiscriminate ANCA testing,
highly active antiretroviral therapy (HAART) era, with 75.6% of tests done outside of guideline
Koderisch et al. described c-ANCA positivity in indications, and duplicate testing, with large cost
24 out of 29 HIV-infected patients (83.0%) [16]. implications. We also demonstrated false positive
More recently, among HIV patients with a well- tests resulting in a lower PPV than described
controlled viral load on HAART, 45.0% had at least elsewhere. Implementing restrictive protocols
one autoantibody present, especially ANA (33.0%) for ANCA testing according to the 1999 testing
and ANCA (13.0%), without clinically relevant guidelines, together with the training of clinicians,
disease [17]. is likely to reduce unnecessary tests, resulting
In the present study, 11.5% of false positive
ANCA tests were observed in patients with in significant cost savings and a reduction in
inappropriate referrals to sub-specialists.
autoimmune diseases, which are consistent with
findings reported elsewhere, particularly among Acknowledgments
patients with chronic autoimmune hepatitis
(70.0%), rheumatoid arthritis, and systemic The authors thank Dr. Nasreen Akoo and Dr. Leandi
lupus erythematosus (20.0%) [18]. Other causes Steynfaardt for assistance with data collection and
of positive ANCA results, including certain Dr. Misha Jivan for statistical analysis.
medications (anti-thyroid drugs, propylthiouracil,
levamisole-adulterated cocaine, minocycline and Funding
hydralazine), and inflammatory bowel disease, None.
have been described but were not encountered in
our study. The high rate of false positive results Conflict of Interest

underscores the need to increase the pre-test
probability by limiting ANCA testing to the 1999 The authors declare that there are no conflicts of
international consensus statement guidelines. interest.
Our study shows a very low rate of PR3 positivity: Author Contributions
only nine patients in the false-positive group and
one in the confirmed AAV group tested positive Conceptualization: All authors
for PR3. We believe that this finding reflects the Investigation: All authors
low rate of positive tests in African populations. Writing-original draft: All authors
Therefore, we plan to conduct more prospective Writing-review and editing: All authors
studies to further investigate this phenomenon. Ethics Approval and Consent to Participate
The AAV group was predominantly RLV, with
half of these patients showing positive ANCA Ethics approval was obtained for this study from
serology. Elsewhere, ANCA-negative RLV has The Human Research Ethics Committee of the
been well-documented, highlighting the importance Faculty of Health Sciences, University of Cape

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