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False-positive diagnosis of tuberculosis with PCR
THE LANCET 1
2 3
Soufer R, Wohlgelernter D, Vita NA, et al. Intact systolic left ventricular function in clinical congestive heart failure. Am J Cardiol 1985; 55: 1032–36. Mair FS, Bundred PE. The diagnosis and management of heart failure: GP opinions. Br J Cardiol 1993; 3: 121–25. Wilhelmsen L. Salt and hypertension. Clin Sci 1979; 57: 455S–58S.
False-positive diagnosis of tuberculosis with PCR SIR—Recent articles describe the usefulness of PCR in diagnosing active tuberculosis.1,2 As amplification of mycobacterial DNA by PCR is increasingly used as a routine method, we would like to emphasise that this test should be applied with great caution in clinical medicine. In certain situations the uncritical interpretation of PCR results might even be harmful to the patient. A 42-year-old white man presented with dyspnoea and fatigue to another hospital. A chest radiograph showed massive left-sided pleural effusion without any other abnormalities. Thoracocentesis revealed a haemorrhagic exudate with a high lymphocyte count and increased lactate dehydrogenase and total protein. Staining and cultures for Mycobacterium tuberculosis were negative, but PCR analyses of pleural fluid with primers specific for insertion sequence 6110 of the M tuberculosis complex (M tuberculosis, africanum, bovis, BCG)3 were positive on two different occasions. As there was absolute peripheral blood lymphocytosis, a bone marrow biopsy was done and the specimen showed B-cell chronic lymphocytic leukaemia (CLL). Because of the PCR results antituberculosis therapy was commenced with rifampicin, isoniazid, and pyrazinamide, but treatment for CLL was postponed. Since the pleural effusion did not resolve after almost 9 months and thoracocentesis had to be carried out repeatedly, the patient was referred to the Department of Internal Medicine at Karl-FranzensUniversity. FACS analysis showed the lymphocytes of the pleural effusion to be positive for CD5 and CD19, and negative for CD3, CD4, and CD8. Furthermore, PCR analyses showed identical patterns of immunoglobulin heavy chain gene rearrangements in pleural, peripheral blood, and bone marrow lymphocytes consistent with the diagnosis of pleural infiltration by CLL. With standard diagnostic tools there was no evidence of pleural tuberculosis. However, PCR for M tuberculosis remained positive. Antituberculous treatment was discontinued and high-dose chemotherapy (potentially curative for CLL) was begun. 10 days after the patient had received a cycle of Dexa-BEAM chemotherapy (dexamethasone, carmustine, etoposide, cytosine arabinoside, melphalan) he became increasingly dyspnoeic. The chest radiograph showed homogenous opacification of the left hemithorax. Thoracocentesis at this time showed a haemorrhagic exudate. This was interpreted as a reaction to high-dose chemotherapy because no lymphocytes could be detected and no evidence of pleural tuberculosis was found. Subsequently, the pleural effusion disappeared and did not recur. Restaging showed the patient to be in remission with a residual bone marrow infiltration of less than 5%. A second course of chemotherapy was begun and at present the patient is awaiting autologous stem cell transplantation. 6 months after discontinuation of the antituberculous therapy there is no evidence of active tuberculosis. This case demonstrates that the results of PCR assays— although highly specific and sensitive for the detection of mycobacterial DNA—should be interpreted only in conjunction with clinical information in order to avoid inappropriate treatment. PCR assays are not standardised; false-positive results may be due to individual laboratory
1388
procedures, contamination, or might reflect amplification of DNA from nonviable mycobacteria.4 In conclusion, diagnosis of active pleural tuberculosis should still include the results of well-established techniques including stains for acid-fast bacilli, culture of mycobacteria, and histological examination of tissue specimens. Martin Trinker, Gerald Höfler, *Heinz Sill *Department of Internal Medicine and Institute of Pathology, Karl-FranzensUniversity, A-8036 Graz, Austria
1
2
3
4
Condos R, McClune A, Rom WN, Schluger NW. Peripheral-bloodbased PCR assay to identify patients with active pulmonary tuberculosis. Lancet 1996; 347: 1082–85. Pfyffer GE, Kissling P, Jahn EMI, Welscher HM, Salfinger M, Weber R. Diagnostic performance of amplified mycobacterium tuberculosis direct test with cerebrospinal fluid, other nonrespiratory, and respiratory specimens. J Clin Microbiol 1996; 34: 834–41. Walker DA, Tayler IK, Mitchell DM, Shaw RJ. Comparison of polymerase chain reaction amplification of two mycobacterial DNA sequences, IS 6110 and the 65 kD antigen gene, in the diagnosis of tuberculosis. Thorax 1992; 47: 690–94. de Wit D, Maartens G, Steyn L. A comparative study of the polymerase chain reaction and conventional procedures for the diagnosis of tuberculous pleural effusion. Tuber Lung Dis 1992; 73: 262–67.
Chronic bronchitis and risk of coronary heart disease SIR—Jousilahti and colleagues (Aug 31, p 567)1 report a significant independent association between longstanding symptoms of chronic bronchitis and the risk of coronary heart disease (CHD) in middle-aged Finnish men and women, mean age 43 years, followed for 13 years. We would like to present findings in elderly patients that extend these results. The Dubbo Study is a continuing prospective study of cardiovascular disease in an elderly Australian cohort first examined in 1988–89.2,3 The cohort consists of all citizens of this town born before 1930 (average age 70 years). Baseline examinations encompassed demographic, psychosocial, and putative cardiovascular risk factors. We did not administer a chronic bronchitis questionnaire, but peak expiratory flow rate (PEFR) was assessed with the Wright peak flow meter. We have grouped PEFR into sex-specific tertiles. CHD events refer to hospital admissions with any manifestation of CHD (ICD-9-CM codes 410-414). The table shows the CHD rates by tertile of PEFR over a median follow-up of 83 months. Men and women belonging to tertile I of PEFR (ie, those having the most airways obstruction) had the highest CHD event and mortality rates. The risk ratio of CHD by PEFR was computed with a proportional hazards model which adjusted (a) for age only, and (b) for age and other major risk factors and confounders2 (CHD at study entry, blood pressure, cigarette smoking, diabetes, various lipids and Men (n=1227) CHD events Peak expiratory flow rate Tertile I (rate/100) 30·8 Tertile II 26·4 Tertile III 22·2 Risk ratio tert I 1·43 vs tert III* (95% CI) (1·08–1·89) Risk ratio tert I 1·21 vs tert III† (95% CI) (0·89–1·64)
Women (n=1541) CHD deaths
CHD events
CHD deaths
11·7 10·8 4·3 2·60 (1·49–4·52) 1·96 (1·08–3·56)
30·1 18·4 13·7 1·66 (1·23–2·25) 1·21 (0·87–1·68)
11·8 5·1 2·2 3·63 (1·87–7·02) 3·16 (1·53–6·54)
*Adjusted for age. †Adjusted for age and other risk factors or confounders.
Table: CHD rates in men and women
Vol 348 • November 16, 1996
2 3
Soufer R, Wohlgelernter D, Vita NA, et al. Intact systolic left ventricular function in clinical congestive heart failure. Am J Cardiol 1985; 55: 1032–36. Mair FS, Bundred PE. The diagnosis and management of heart failure: GP opinions. Br J Cardiol 1993; 3: 121–25. Wilhelmsen L. Salt and hypertension. Clin Sci 1979; 57: 455S–58S.
False-positive diagnosis of tuberculosis with PCR SIR—Recent articles describe the usefulness of PCR in diagnosing active tuberculosis.1,2 As amplification of mycobacterial DNA by PCR is increasingly used as a routine method, we would like to emphasise that this test should be applied with great caution in clinical medicine. In certain situations the uncritical interpretation of PCR results might even be harmful to the patient. A 42-year-old white man presented with dyspnoea and fatigue to another hospital. A chest radiograph showed massive left-sided pleural effusion without any other abnormalities. Thoracocentesis revealed a haemorrhagic exudate with a high lymphocyte count and increased lactate dehydrogenase and total protein. Staining and cultures for Mycobacterium tuberculosis were negative, but PCR analyses of pleural fluid with primers specific for insertion sequence 6110 of the M tuberculosis complex (M tuberculosis, africanum, bovis, BCG)3 were positive on two different occasions. As there was absolute peripheral blood lymphocytosis, a bone marrow biopsy was done and the specimen showed B-cell chronic lymphocytic leukaemia (CLL). Because of the PCR results antituberculosis therapy was commenced with rifampicin, isoniazid, and pyrazinamide, but treatment for CLL was postponed. Since the pleural effusion did not resolve after almost 9 months and thoracocentesis had to be carried out repeatedly, the patient was referred to the Department of Internal Medicine at Karl-FranzensUniversity. FACS analysis showed the lymphocytes of the pleural effusion to be positive for CD5 and CD19, and negative for CD3, CD4, and CD8. Furthermore, PCR analyses showed identical patterns of immunoglobulin heavy chain gene rearrangements in pleural, peripheral blood, and bone marrow lymphocytes consistent with the diagnosis of pleural infiltration by CLL. With standard diagnostic tools there was no evidence of pleural tuberculosis. However, PCR for M tuberculosis remained positive. Antituberculous treatment was discontinued and high-dose chemotherapy (potentially curative for CLL) was begun. 10 days after the patient had received a cycle of Dexa-BEAM chemotherapy (dexamethasone, carmustine, etoposide, cytosine arabinoside, melphalan) he became increasingly dyspnoeic. The chest radiograph showed homogenous opacification of the left hemithorax. Thoracocentesis at this time showed a haemorrhagic exudate. This was interpreted as a reaction to high-dose chemotherapy because no lymphocytes could be detected and no evidence of pleural tuberculosis was found. Subsequently, the pleural effusion disappeared and did not recur. Restaging showed the patient to be in remission with a residual bone marrow infiltration of less than 5%. A second course of chemotherapy was begun and at present the patient is awaiting autologous stem cell transplantation. 6 months after discontinuation of the antituberculous therapy there is no evidence of active tuberculosis. This case demonstrates that the results of PCR assays— although highly specific and sensitive for the detection of mycobacterial DNA—should be interpreted only in conjunction with clinical information in order to avoid inappropriate treatment. PCR assays are not standardised; false-positive results may be due to individual laboratory
1388
procedures, contamination, or might reflect amplification of DNA from nonviable mycobacteria.4 In conclusion, diagnosis of active pleural tuberculosis should still include the results of well-established techniques including stains for acid-fast bacilli, culture of mycobacteria, and histological examination of tissue specimens. Martin Trinker, Gerald Höfler, *Heinz Sill *Department of Internal Medicine and Institute of Pathology, Karl-FranzensUniversity, A-8036 Graz, Austria
1
2
3
4
Condos R, McClune A, Rom WN, Schluger NW. Peripheral-bloodbased PCR assay to identify patients with active pulmonary tuberculosis. Lancet 1996; 347: 1082–85. Pfyffer GE, Kissling P, Jahn EMI, Welscher HM, Salfinger M, Weber R. Diagnostic performance of amplified mycobacterium tuberculosis direct test with cerebrospinal fluid, other nonrespiratory, and respiratory specimens. J Clin Microbiol 1996; 34: 834–41. Walker DA, Tayler IK, Mitchell DM, Shaw RJ. Comparison of polymerase chain reaction amplification of two mycobacterial DNA sequences, IS 6110 and the 65 kD antigen gene, in the diagnosis of tuberculosis. Thorax 1992; 47: 690–94. de Wit D, Maartens G, Steyn L. A comparative study of the polymerase chain reaction and conventional procedures for the diagnosis of tuberculous pleural effusion. Tuber Lung Dis 1992; 73: 262–67.
Chronic bronchitis and risk of coronary heart disease SIR—Jousilahti and colleagues (Aug 31, p 567)1 report a significant independent association between longstanding symptoms of chronic bronchitis and the risk of coronary heart disease (CHD) in middle-aged Finnish men and women, mean age 43 years, followed for 13 years. We would like to present findings in elderly patients that extend these results. The Dubbo Study is a continuing prospective study of cardiovascular disease in an elderly Australian cohort first examined in 1988–89.2,3 The cohort consists of all citizens of this town born before 1930 (average age 70 years). Baseline examinations encompassed demographic, psychosocial, and putative cardiovascular risk factors. We did not administer a chronic bronchitis questionnaire, but peak expiratory flow rate (PEFR) was assessed with the Wright peak flow meter. We have grouped PEFR into sex-specific tertiles. CHD events refer to hospital admissions with any manifestation of CHD (ICD-9-CM codes 410-414). The table shows the CHD rates by tertile of PEFR over a median follow-up of 83 months. Men and women belonging to tertile I of PEFR (ie, those having the most airways obstruction) had the highest CHD event and mortality rates. The risk ratio of CHD by PEFR was computed with a proportional hazards model which adjusted (a) for age only, and (b) for age and other major risk factors and confounders2 (CHD at study entry, blood pressure, cigarette smoking, diabetes, various lipids and Men (n=1227) CHD events Peak expiratory flow rate Tertile I (rate/100) 30·8 Tertile II 26·4 Tertile III 22·2 Risk ratio tert I 1·43 vs tert III* (95% CI) (1·08–1·89) Risk ratio tert I 1·21 vs tert III† (95% CI) (0·89–1·64)
Women (n=1541) CHD deaths
CHD events
CHD deaths
11·7 10·8 4·3 2·60 (1·49–4·52) 1·96 (1·08–3·56)
30·1 18·4 13·7 1·66 (1·23–2·25) 1·21 (0·87–1·68)
11·8 5·1 2·2 3·63 (1·87–7·02) 3·16 (1·53–6·54)
*Adjusted for age. †Adjusted for age and other risk factors or confounders.
Table: CHD rates in men and women
Vol 348 • November 16, 1996