Apers L, Mutsvangwa J, Magwenzi J, Chigara N, Butterworth A, Mason P, Van der Stuyft P
Department of Epidemiology, Provincial Medical Directorate, Epidemiology, Gweru, Midlands, Zimbabwe.
Int J Tuberc Lung Dis. 2003 Apr;7(4):376-81.
In countries with high human immunodeficiency virus prevalence, laboratory diagnosis of pulmonary tuberculosis with the standard Ziehl-Neelsen (ZN) technique is characterised by low sensitivity.
To compare test characteristics of direct microscopy, the concentration method and the Mycobacteria Growth Indicator Tube (MGIT).
Three hundred specimens from patients diagnosed with pulmonary tuberculosis were tested for the presence of mycobacteria. Specimens were stained with ZN, decontaminated by adding 4% NaOH, concentrated by centrifuging and processed in MGIT broth. The gold standard was defined as a positive MGIT culture or a positive acid-fast bacilli smear of material obtained from a negative culture after 42 days.
A total of 44 (14.7%) specimens were contaminated. Of 256 valid specimens, 234 (91.4%) were positive according to the gold standard definition. Decontamination and concentration of the sample increased the sensitivity of direct microscopy from 67.5% to 87.1%. Specificity remained unchanged (95.5%). The overall median time to detection of MGIT culture-positive specimens was 5 days, ranging from 4 (direct smear-positive specimens) to 12 days (concentration smear-negative specimens).
The concentration method substantially increases the sensitivity of direct microscopy without much extra input. The MGIT culture technique has considerable advantages, but its relatively high contamination rate and its high cost make it a less recommendable option for widespread use in routine district laboratories.
在人类免疫缺陷病毒感染率较高的国家，采用标准的萋-尼（ZN）技术对肺结核进行实验室诊断，其敏感性较低。
比较直接显微镜检查、浓缩法和分枝杆菌生长指示管（MGIT）的检测特性。
对300例确诊为肺结核患者的标本进行分枝杆菌检测。标本用ZN染色，加入4%氢氧化钠进行去污处理，通过离心进行浓缩，并在MGIT肉汤中进行处理。金标准定义为MGIT培养阳性或42天后从阴性培养物中获得的材料抗酸杆菌涂片阳性。
共有44份（14.7%）标本被污染。在256份有效标本中，根据金标准定义，有234份（91.4%）为阳性。样本的去污和浓缩使直接显微镜检查的敏感性从67.5%提高到87.1%。特异性保持不变（95.5%）。MGIT培养阳性标本的总体中位检测时间为5天，范围从4天（直接涂片阳性标本）到12天（浓缩涂片阴性标本）。
浓缩法在没有太多额外投入的情况下大幅提高了直接显微镜检查的敏感性。MGIT培养技术有相当多的优点，但其相对较高的污染率和高成本使其不太适合在常规地区实验室广泛使用。
