Patwardhan S A, Bhargava P, Bhide V M, Kelkar D S
Consultant Microbiologist, Deenanath Mangeshkar Hospital and Research Centre, Erandawane, Pune, India.
Indian J Med Microbiol. 2011 Oct-Dec;29(4):389-94. doi: 10.4103/0255-0857.90173.
The purpose of our study was to compare various laboratory diagnostic methods, namely histopathological examination, Ziehl-Neelsen (ZN) stain, AFB culture by conventional Lowenstein-Jensen (LJ) method and fluorescence-based mycobacterial growth indicator tube (MGIT) technique and polymerase chain reaction (PCR) in clinically suspected cases of tubercular lymphadenitis.
A total of 65 lymph nodes biopsied from patients clinically suspected of having tubercular lymph nodes were included. Specimens were processed for AFB culture after NaOH-NALC concentration and inoculation on LJ medium and using the MGIT system. PCR was performed on all specimens using a commercial nested PCR kit targeting IS6110 insertion element of Mycobacterium tuberculosis complex. All lymph node specimens were subjected to histopathological examination.
Of the 65 lymph nodes, 37 (56.9%) were positive on MGIT culture and 45 (69.2%) were positive by PCR. Histopathology showed maximum sensitivity (96%) but with compromised specificity (78.5%). PCR showed 90.1% sensitivity and 100% specificity. The mean turnaround time for mycobacterial growth in smear negative specimens was 30 days determined by LJ and 20 days by MGIT techniques.
PCR is a rapid and useful method for diagnosis of TB lymphadenitis and definitely increases the positive predictive value of a positive histopathology report. MGIT is better than LJ culture as regards time to positivity and higher yield.
我们研究的目的是比较各种实验室诊断方法，即组织病理学检查、萋-尼（ZN）染色、传统罗氏（LJ）培养基培养法进行抗酸杆菌（AFB）培养、基于荧光的分枝杆菌生长指示管（MGIT）技术以及聚合酶链反应（PCR），用于临床疑似结核性淋巴结炎的病例。
纳入了总共65例从临床疑似结核性淋巴结的患者身上获取的淋巴结活检样本。样本经氢氧化钠- N-乙酰-L-半胱氨酸（NaOH-NALC）浓缩后进行AFB培养，并接种于LJ培养基及使用MGIT系统。使用针对结核分枝杆菌复合群IS6110插入元件的商业巢式PCR试剂盒对所有样本进行PCR检测。所有淋巴结样本均进行组织病理学检查。
在65个淋巴结中，37个（56.9%）在MGIT培养中呈阳性，45个（69.2%）通过PCR呈阳性。组织病理学显示出最高的敏感性（96%），但特异性有所降低（78.5%）。PCR显示敏感性为90.1%，特异性为100%。涂片阴性样本中分枝杆菌生长的平均周转时间，LJ法测定为30天，MGIT技术测定为20天。
PCR是诊断结核性淋巴结炎的一种快速且有用的方法，确实提高了阳性组织病理学报告的阳性预测值。就阳性所需时间和更高的检出率而言，MGIT优于LJ培养法。
