A new algorithm for histopathological diagnosis of periprosthetic infection using CD15 focus score and computer program CD15 Quantifier

Introduction. A simple microscopic diagnostic quantification system for neutrophile granulocytes (NG) was developed evaluating a single focal point (CD15 focus score) which enables the detection of bacterial infection in SLIM (synoviallike interface membrane) Additionally a diagnostic algorithm is proposed how to use the CD15 focus score and the quantification software (CD15 Quantifier). Methods. 91 SLIM removed during revision surgery for histopathological diagnosis (hip; n=59 and knee; n=32) underwent histopathological classification according to the SLIM-consensus classification. NG where identified immunohistochemically by means of a CD15-specific monoclonal antibody exhibiting an intense granular cytoplasmic staining pattern. This pattern is different from CD15 expression in macrophages showing a pale and homogenous expression in mononuclear cells. The quantitative evaluation of CD15-positive neutrophils granulocytes (CD15NG) used the principle of maximum focal infiltration (focus) together with an assessment of a single focal point (approximately 0.3 mm²). This immunohistochemical data made it possible to develop CD15 Quantifier software which automatically quantifies CD15NG. Results. SLIM-cases with positive microbiological diagnosis (n=47) have significantly (p<0.001, Mann-Whitney U test) more CD15NG/focal point than cases with negative microbiological diagnosis (n=44). 50 CD15NG/focal point were identified as the optimum threshold when diagnosing infection of periprosthetic joints using the CD15 focus score. If the microbiological findings are used as a ‘gold standard’ the diagnostic sensitivity is 0.83, specificity is 0.864. (PPV: 0.87; NPV: 0.83; accuracy 0.846; AUC: 0.878.) The evaluation findings for the preparations using the CD15 Quantifier (n=31) deviated in an average of 12 cells from the histopathological evaluation findings (CD15focus score). From a cell-count greater 62 CD15 Quantifier needs on average 32 seconds less than the diagnostic pathologist. Conclusion. The CD15 focus score, and the use of the «CD15 Quantifier» software which is thereby made possible, offers an automated procedure which shortens the mentally tiring and time-consuming process of microscopic cell-counting. The proposed diagnostic algorithm (how to use the CD15 focus score and the quantification software, CD15 Quantifier) may contribution towards the standardisation for periprosthetic joint infection and diagnosing bacterial infections in the SLIM.

метод CD15 focus score, диагностика перипротезной инфекции, автоматический количественный анализ, классификация SLIM-консенсуса, CD15 focus score, periprosthetic joint infection, automated image analysis, SLIM-Consensus-classification