Van Deun A, Salim A Hamid, Cooreman E, Daru P, Das A P K, Aung K J M, Rieder H L
Mycobacteriology Unit, Institute of Tropical Medicine, Antwerp, Belgium.
Int J Tuberc Lung Dis. 2004 Jul;8(7):816-23.
A tuberculosis control project in Bangladesh.
To document the frequency and diagnostic value of smears with scanty acid-fast bacilli (AFB) (IUATLD/WHO scale, < 10/100 high power fields), and to assess the appropriateness of the current positivity threshold.
Analysis of databases of laboratory registers, patient records and the diagnostic yield of sputum collection strategies.
Scanty smears constituted about 10% of suspect and almost 50% of follow-up smears. In suspect series, 10% of scanty 1-9/100 were not confirmed by another positive or scanty AFB sputum, compared to 7.5% of results at the current cut-off value of 10/100. Considering such results as positive by adopting a lower cut-off as low as the 1/100 used in the ATS scale added 1.5% false positives at the most. In return, the gain in confirmed positive cases was up to 10%, and that in positive results exceeded the incremental yield of the third diagnostic sputum. Significance of scanty follow-up smears at the end of the intensive phase was suggested by their association with treatment failure and unfavourable outcome overall.
Scanty results (IUATLD/WHO scale) are not rare and should not be ignored. Adoption of a considerably lower positivity threshold would be appropriate in control programmes where basic conditions for reliable AFB microscopy, including regular quality assessment, are present.
孟加拉国的一个结核病控制项目。
记录涂片上抗酸杆菌（AFB）数量稀少（国际防痨和肺部疾病联合会/世界卫生组织标准，每100个高倍视野中<10个）的频率和诊断价值，并评估当前阳性阈值的合理性。
对实验室登记数据库、患者记录以及痰标本采集策略的诊断产出进行分析。
少量涂片约占疑似病例涂片的10%，几乎占随访涂片的50%。在疑似病例系列中，每100个视野中有1 - 9个抗酸杆菌的少量涂片结果中，10%未被另一份阳性或少量AFB痰标本结果所证实，而当前截断值为每100个视野中10个时，这一比例为7.5%。采用低至美国胸科学会（ATS）标准中每100个视野中1个的更低截断值将此类结果判定为阳性，最多增加1.5%的假阳性。作为回报，确诊阳性病例增加了10%，阳性结果的增加超过了第三次诊断性痰标本的增量产出。强化期结束时少量随访涂片与治疗失败及总体不良结局相关，提示了其重要性。
少量结果（国际防痨和肺部疾病联合会/世界卫生组织标准）并不罕见，不应被忽视。在具备包括定期质量评估在内的可靠AFB显微镜检查基本条件的控制项目中，采用低得多的阳性阈值是合适的。
