Njau Allan N, Gakinya Samuel M, Sayed Shahin, Moloo Zahir
Department of Pathology and Laboratory Medicine, Aga Khan University Hospital, Nairobi, Kenya.
Afr J Lab Med. 2019 Sep 18;8(1):748. doi: 10.4102/ajlm.v8i1.748. eCollection 2019.
Diagnosis of extrapulmonary tuberculosis continues to be a challenge due to the complexity of the causative organism and the wide array of pathologic features seen in this infection. Xpert MTB/RIF can be used on fresh or frozen tissue specimens for diagnosis of tuberculosis with good results. However, there is little data on its use with formalin-fixed paraffin-embedded (FFPE) tissues.
The aim of this study was to demonstrate the potential utility of Xpert MTB/RIF and to compare its performance to Ziehl-Neelsen staining for the detection of from FFPE tissues using histological features from haematoxylin and eosin staining as the gold standard.
Eighty randomly selected archival FFPE tissues exhibiting histological features of tuberculosis were included in the study. After deparaffinisation and lysis, all the tissue specimens were subjected to the Xpert MTB/RIF assay. The outcome measures were proportions of positively identified cases by each test.
Using histology as the gold standard, the sensitivity of Ziehl-Neelsen staining was 20.3% (95% confidence interval: 12% - 30.8%), and the sensitivity of the Xpert MTB/RIF assay was 53.2% (95% confidence interval: 41.6% - 64.9%); the difference was statistically significant ( = 0.002). None of the cases tested positive for rifampicin resistance.
With prior deparaffinisation and lysis, FFPE tissues are amenable to testing by Xpert MTB/RIF assay. A validation study to determine the clinical utility, analytical optimisation and cost implications of this assay for FFPE tissues is recommended.
由于致病生物体的复杂性以及该感染中所见的广泛病理特征，肺外结核的诊断仍然是一项挑战。Xpert MTB/RIF可用于新鲜或冷冻组织标本以诊断结核病，效果良好。然而，关于其在福尔马林固定石蜡包埋（FFPE）组织中的应用数据很少。
本研究的目的是证明Xpert MTB/RIF的潜在效用，并将其性能与齐-尼氏染色进行比较，以苏木精和伊红染色的组织学特征作为金标准，检测FFPE组织中的结核分枝杆菌。
本研究纳入了80份随机选择的具有结核病组织学特征的存档FFPE组织。经过脱蜡和裂解后，所有组织标本均进行Xpert MTB/RIF检测。结果指标是每种检测方法阳性鉴定病例的比例。
以组织学作为金标准，齐-尼氏染色的敏感性为20.3%（95%置信区间：12% - 30.8%），Xpert MTB/RIF检测的敏感性为53.2%（95%置信区间：41.6% - 64.9%）；差异具有统计学意义（P = 0.002）。所有病例的利福平耐药检测均为阴性。
经过预先脱蜡和裂解后，FFPE组织适合通过Xpert MTB/RIF检测进行检测。建议进行一项验证研究，以确定该检测方法对FFPE组织的临床效用、分析优化和成本影响。
