Kothadia S N, Deshmukh S, Saoji A M
Department of Microbiology, Dr. V.M. Medical College, Solapur.
Indian J Pathol Microbiol. 1990 Jan;33(1):68-73.
A 'false case' in reference to pulmonary tuberculosis is designated as one where, the primary smear shows presence of Acid Fast Bacilli (AFB). However, the subsequent cultural examination fails to grow the pathogen. The present study is directed to determine the incidence of false positivity and attempt its correlation with the number of bacilli in the primary smear, age of the patient and chemotherapy. Of the 820 sputum samples processed, 14.63 percent revealed presence of bacilli both in smear and by cultural examination (true positive), 64.02 percent were true negative (smear and culture negative), 15.97 percent were false negative (smear negative culture positive) while 5.36 percent displayed false positivity. The data analysis has further revealed an inverse relationship between the number of bacilli in the entire smear and false positivity. Aged patients (more than 40 years) who were on prolonged and irregular antitubercular therapy showed a higher incidence of false positivity (50 percent) as compared to others. The present study has indicated that primary scrutiny of the smear should be done with due care and a due consideration should be given to clinical presentation, radiological findings and account of chemotherapy while assessing the prognosis. We further recommend that every sample should be simultaneously processed for cultural examination to avoid the false positivity, if any.
肺结核的“假病例”是指初次涂片显示有抗酸杆菌（AFB），但随后的培养检查未能培养出病原体的情况。本研究旨在确定假阳性的发生率，并尝试将其与初次涂片中杆菌数量、患者年龄和化疗情况相关联。在处理的820份痰标本中，14.63%的标本涂片和培养检查均显示有杆菌（真阳性），64.02%为真阴性（涂片和培养均为阴性），15.97%为假阴性（涂片阴性培养阳性），而5.36%显示为假阳性。数据分析进一步揭示了整个涂片中杆菌数量与假阳性之间呈反比关系。与其他患者相比，年龄较大（40岁以上）且接受长期不规则抗结核治疗的患者假阳性发生率更高（50%）。本研究表明，在评估预后时，应谨慎进行涂片的初步检查，并充分考虑临床表现、影像学检查结果和化疗情况。我们进一步建议，每个样本都应同时进行培养检查，以避免出现假阳性（如有）。
