Manson Unit, Médecins Sans Frontières UK, 67-74 Saffron Hill, London EC1N 8QX, UK.
BMC Infect Dis. 2010 Sep 21;10:276. doi: 10.1186/1471-2334-10-276.
Diagnostic options for pulmonary tuberculosis in resource-poor settings are commonly limited to smear microscopy. We investigated whether bleach concentration by sedimentation and sputum cytology analysis (SCA) increased the positivity rate of smear microscopy for smear-positive tuberculosis.
We did a prospective diagnostic study in a Médecins Sans Frontières-supported hospital in Mindouli, Republic of Congo. Three sputum samples were obtained from 280 consecutive pulmonary tuberculosis suspects, and were processed according to WHO guidelines for direct smear microscopy. The remainder of each sputum sample was homogenised with 2.6% bleach, sedimented overnight, smeared, and examined blinded to the direct smear result for acid-fast bacilli (AFB). All direct smears were assessed for quality by SCA. If a patient produced fewer than three good-quality sputum samples, further samples were requested. Sediment smear examination was performed independently of SCA result on the corresponding direct smear. Positivity rates were compared using McNemar's test.
Excluding SCA, 43.2% of all patients were diagnosed as positive on direct microscopy of up to three samples. 47.9% were diagnosed on sediment microscopy, with 48.2% being diagnosed on direct microscopy, sediment microscopy, or both. The positivity rate increased from 43.2% to 47.9% with a case definition of one positive smear (≥1 AFB/100 high power fields) of three, and from 42.1% to 43.9% with two positive smears. SCA resulted in 87.9% of patients producing at least two good-quality sputum samples, with 75.7% producing three or more. Using a case definition of one positive smear, the incremental yield of bleach sedimentation was 14/121, or 11.6% (95% CI 6.5-18.6, p = 0.001) and in combination with SCA was 15/121, or 12.4% (95% CI 7.1-19.6, p = 0.002). Incremental yields with two positive smears were 5/118, or 4.2% (95% CI 1.4-9.6, p = 0.062) and 7/118, or 5.9% (95% CI 2.4-11.8, p = 0.016), respectively.
The combination of bleach sedimentation and SCA resulted in significantly increased microscopy positivity rates with a case definition of either one or two positive smears. Implementation of bleach sedimentation led to a significant increase in the diagnosis of smear-positive patients. Implementation of SCA did not result in significantly increased diagnosis of tuberculosis, but did result in improved sample quality. Requesting extra sputum samples based on SCA results, combined with bleach sedimentation, could significantly increase the detection of smear-positive patients if routinely implemented in resource-limited settings where gold standard techniques are not available. We recommend that a pilot phase is undertaken before routine implementation to determine the impact in a particular context.
在资源匮乏的环境中，用于诊断肺结核的诊断方案通常仅限于痰涂片镜检。我们研究了沉淀法漂白剂浓度和痰细胞学分析（SCA）是否会增加阳性肺结核的涂片阳性率。
我们在刚果共和国芒杜利的无国界医生组织支持的医院进行了一项前瞻性诊断研究。连续 280 例疑似肺结核患者采集 3 份痰标本，按照世界卫生组织直接涂片显微镜检查指南进行处理。每份痰标本的其余部分用 2.6%的漂白剂混合，沉淀过夜，涂抹，然后在不了解直接涂片结果的情况下，用盲法检查抗酸杆菌（AFB）。所有直接涂片均进行 SCA 质量评估。如果患者产生的高质量痰标本少于 3 份，则要求进一步采样。沉淀涂片检查是在相应的直接涂片的 SCA 结果之外独立进行的。使用 McNemar 检验比较阳性率。
排除 SCA，所有患者中有 43.2%的人通过最多 3 份样本的直接显微镜检查被诊断为阳性。47.9%的人通过沉淀显微镜检查确诊，48.2%的人通过直接显微镜检查、沉淀显微镜检查或两者均确诊。当病例定义为 3 份样本中至少有 1 份阳性（≥1 AFB/100 高倍视野）时，阳性率从 43.2%增加到 47.9%，当病例定义为 2 份阳性时，阳性率从 42.1%增加到 43.9%。SCA 使 87.9%的患者至少产生了 2 份高质量的痰标本，其中 75.7%的患者产生了 3 份或更多。使用 1 份阳性涂片的病例定义，漂白沉淀的增量检出率为 14/121，即 11.6%（95%CI 6.5-18.6，p=0.001），与 SCA 联合使用的增量检出率为 15/121，即 12.4%（95%CI 7.1-19.6，p=0.002）。用 2 份阳性涂片的增量检出率为 5/118，即 4.2%（95%CI 1.4-9.6，p=0.062）和 7/118，即 5.9%（95%CI 2.4-11.8，p=0.016）。
用 1 份或 2 份阳性涂片的病例定义，结合漂白沉淀和 SCA 可显著提高显微镜阳性率。实施漂白沉淀可显著增加阳性涂片患者的诊断率。实施 SCA 并未显著增加结核病的诊断率，但确实提高了标本质量。如果在无法获得金标准技术的资源有限的环境中常规实施，根据 SCA 结果要求额外的痰标本，并结合漂白沉淀，可显著提高阳性涂片患者的检出率。我们建议在常规实施前进行试点阶段，以确定在特定环境中的影响。
