| ORIGINAL ARTICLE |
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| Year : 2012 | Volume
: 7
| Issue : 4 | Page : 209-214 |
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Determining the prevalence of antineutrophil cytoplasmic antibody and the cut-offs of anti-PR3 and anti-MPO antibody in general population
Parasar Ghosh, Sanjay Dwivedi, Ramnath Misra, Vikas Agarwal
Department of Clinical Immunology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow 226014, India
Correspondence Address:
Vikas Agarwal
Department of Clinical Immunology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow 226014
India
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.1016/j.injr.2012.09.006
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Objectives: Antineutrophil cytoplasmic antibodies (ANCAs) are serological hallmark of ANCA associated vasculitides (AAV); Wegener's granulomatosis (WG), Microscopic polyangiitis (MPA) and ChurgeStrauss Syndrome. Conven- tionally, ANCA test is carried out on human neutrophils by indirect immunofluorescence (IIF) and antigenic determinant is confirmed with specific ELISA. Since most of the ELISA kits are manufactured outside India and cut-offs provided by the manufacturers are based on different ethnic population, their diagnostic performance may vary. Therefore, we aimed to define the optimum cut-off values that distinguish between the patient and healthy individual in Indian population.
Methods: Sera of patients with AAV, and healthy individuals were tested for anti-Proteinase 3 (PR3) and -Myelo- peroxidase (MPO) using commercially available ELISA kits. Receiver operator characteristics (ROCs) curve was constructed to define the optimum cut-off value between the patients and healthy individuals.
Results: ANCA was performed on 280 sera from healthy individuals, and 22 patients with active WG and 11 with active MPA. In healthy individuals, ANCA at dilutions 1:40, 1:80, 1:160, and 1:320 was positive in 7.14, 3.9, 1, and
0.3% respectively. ROC curves analysis showed that for PR3-ANCA antibody the best cut-off was 19 RU/ml at which the sensitivity was 81.8% and specificity was 100%. Similarly, for MPO-ANCA antibody, the best cut-off was
14.95 RU/ml at which sensitivity was 90.9% while specificity was 100%. Both of these cut-off values were different than the manufacturer's cut-off values.
Conclusion: Optimization of imported kits as per the local healthy population should be carried out to improve its diagnostic performance. |
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