Poor Adherence to Indications for Anti-neutrophil Cytoplasmic Antibody Testing in a South African Tertiary Hospital

Appropriate use of laboratory investigations is increasingly important in resource-constrained environments. In this study, we reviewed the anti-neutrophil cytoplasmic antibody (ANCA) testing practices in a tertiary hospital in South Africa. A retrospective file review was conducted, encompassing all ANCA tests ordered over 12 months, including both inpatients and outpatients. Sociodemographic and clinical details were extracted from the patient records. All requests were assessed against the International Consensus Statement of 1999, which provides clinical guidelines for the indications for ANCA testing. Of the 945 ANCA tests requested, 790 patient records were reviewed, while 155 records were found to be missing, and 62 patients had multiple tests. Only 193 patients (24.4%) had indications for ANCA testing that met the guidelines. The most common tests done outside guideline indications were critical limb ischemia (9.6%), stroke (7.3%), uveitis (5.7%), renal impairment (4.9%), and interstitial lung disease (4.4%). Among the patients, ten (1.3%) were diagnosed with ANCA-associated vasculitis (AAV), of whom nine had renal-limited vasculitis. Twenty-six patients tested positive for ANCA without any evidence of AAV. Of these false positives, 10 (38.4%) were human immunodeficiency virus (HIV) positive, 3 (11.5%) had tuberculosis (TB), and 3 (11.5%) had other autoimmune diseases. The annual cost of ANCA tests amounted to ZAR274,046, with ZAR17,490 spent on duplicate testing and ZAR208,275 on non-indicated clinical conditions. The study revealed that ANCA testing was performed outside standard guidelines in three-quarters of requests, and duplicate testing was common, resulting in large cost implications. Chronic infections, such as HIV and TB, and autoimmune conditions accounted for half of the false-positive tests. The findings suggest that training of clinicians is likely to reduce unnecessary tests.