- Email: [email protected]
Re: How many sputum specimens are necessary to diagnose pulmonary tuberculosis
328
letters to the Editor
Vol. 34 No. 5
Re: How many sputum specimens are necessary to diagnose pulmonary tuberculosis To the Editor: We published the results of our study conducted at Grady Memorial Hospital (GMH), an urban universityaffiliated public hospital in Atlanta, Georgia, in an article by Leonard et al1 in your journal. The study evaluated sensitivity of acid-fast bacilli (AFB) smears to determine the optimal number of AFB sputum or respiratory specimens necessary to diagnose pulmonary tuberculosis (TB). In our study, we found that, in our institution, 2 respiratory specimens were adequate in establishing a diagnosis of pulmonary TB and that the third specimen added little additional diagnostic value. We received questions from readers regarding the sensitivity of AFB culture. We conducted a follow-up study with the same data with the purpose of determining the diagnostic yield of culture from each sputum specimen. All patients included in the previous reported study in the AJIC1 had 1 or more positive cultures for Mycobacterium tuberculosis recovered from sputum or respiratory specimens between January 1, 1997, and October 1, 2000. During the study period, 425 patients were diagnosed with pulmonary tuberculosis. Complete data on culture results were available on the 409 patients included in our analysis of AFB culture sensitivity. Cultures were performed on 918 respiratory specimens from these 409 patients. A total of 804 (88%) of 918 respiratory specimens were culture positive. Sensitivities of first, second, and third AFB cultures were calculated overall and separately for HIV-seronegative and HIV-seropositive patients. Proportions were compared using the Mantel-Haenszel x2 test and Fisher exact test as appropriate, and the Mantel-Haenszel odds ratios (OR) and corresponding 95% confidence intervals (CI) were calculated.
The overall sensitivity of a positive culture among patients with culture-confirmed tuberculosis increased from 91% with 1 sputum specimen to 98% and 100% with second and third sputum specimens collected, respectively. The sensitivity of the culture for HIVseronegative patients (94%, 99%, and 100% with 1, 2, and 3 smears collected) compared with that for HIV-infected patients (86%, 97%, and 100%, respectively, for 1, 2 and 3 smears collected) is shown in Table 1. The first culture was statistically significantly more sensitive in HIV-seronegative patients compared with HIV-infected patients (P 5 004), but the second culture was not (P 5 14). Pulmonary tuberculosis was diagnosed by the third positive culture when the first and second cultures were negative in 9 of 409 patients (2%) overall: 2 of 228 (1%) in HIV-seronegative patients, 4 of 138 (3%) in HIV-seropositive patients, and 3 of 43 (7%) in patients with unknown HIV status. In 122 of 409 (30%) patients, the first AFB sputum smear was negative, whereas the first culture was positive; in 1 of 409 (0.2%) patients, the first AFB sputum smear was positive, whereas the first AFB culture was negative. A total of 37 (9%) of 409 patients had a negative AFB culture from the first respiratory specimen. We analyzed predictors of needing more than 1 sputum culture for diagnosing pulmonary tuberculosis. Patients with a first positive AFB culture and patients with a first negative AFB culture had similar demographic characteristics. HIV-infected patients with pulmonary TB were more likely to have the first specimen be AFB culture negative compared with HIV-seronegative patients (20/138 [15%] vs 13/228 [6%], respectively; OR, 2.80; 95% CI: 1.35-5.84). Chest roentgenograms results were available for 393 patients. Having a roentgenogram with signs of upper or middle lobe infiltrate (OR, 0.17, 95% CI: 0.06-0.48) or cavitary lesion (OR, 0.04; 95% CI: 0.010.38) was negatively associated with having a first
Table 1. Analysis of sensitivity of acid-fast bacilli cultures from respiratory specimens in patients with culture confirmed pulmonary TB*y Overallz N = 409
HIV negative N = 228
HIV positive N = 138
Culture
Sensitivity, % (95% CI)
Additional benefit in sensitivity, % (95% CI)
Sensitivity, % (95% CI)
Additional benefit in sensitivity, % (95% CI)
Sensitivity, % (95% CI)
Additional benefit in sensitivity, % (95% CI)
1 2 3
91 (88-94) 98 (96-99) 100 (99-100)
7 (5-10) 2 (1-4)
94 (90-97) 99 (97-100) 100 (98-100)
5 (2-8) 1 (0.1-3)
86 (79-91) 97 (93-99) 100 (97-100)
11 (7-18) 3 (1-7)
*Additional benefit of second culture is in comparison with first culture, and additional benefit of third culture is in comparison with second culture. y Exact test was used for calculation of 95% confidence intervals for proportions. z Overall category includes 43 HIV-unknown patients.
letters to the Editor
June 2006
negative AFB culture from a respiratory specimen in univariate analysis (patients with normal roentgenogram were the referent group). In summary, as we found for our analysis of AFB smear,1 the third specimen for AFB culture from a respiratory specimen added little additional diagnostic value in establishing a diagnosis of pulmonary tuberculosis. The overall benefit in sensitivity of the third specimen was 2%, and there was a slightly higher diagnostic value among HIV-infected patients (additional benefit in sensitivity of 3%); the difference among HIV infected and HIV seronegative was statistically significant for the first, but not the second culture. Because our follow-up study was based only on culture-positive cases, we were unable to calculate specificity or negative predictive value for AFB culture. At our institution, 2 specimens proved to be adequate in almost all patients in establishing a diagnosis of pulmonary tuberculosis, and the benefit of the third specimen was of little diagnostic value. Other institutions should evaluate their data because considerable cost savings could be incurred by requiring 2 rather than 3 specimens to evaluate a patient for pulmonary TB. Michael K. Leonard, Jr, MD Ekaterina Kourbatova, MD Henry M. Blumberg, MD Assistant Professor of Medicine Divsion of Infectious Diseases Emory University School of Medicine
329
Reduction in nosocomial infection with improved hand hygiene in intensive care units of a tertiary care hospital in Argentina To the Editor: I wish to bring to your readers’ attention a misinterpretation of results reported in the Discussion section of the article by Rosenthal et al, Reduction in nosocomial infection with improved hand hygiene in intensive care units of a tertiary care hospital in Argentina. Am J Infect Control 2005;33:392-7. The authors’ discussion of our results for increasing hand hygiene compliance through patient empowerment (Partners In Your Care) was incorrectly reported. The objective of the reported study was to determine 2 postintervention phases: (1) no intervention and (2) visual reminder/ no patient empowerment. The study objective was to determine overall sustained compliance from baseline following the 2 postintervention phases. Based on this design, our findings showed an overall sustained increase in compliance of 56% from baseline (P < 001).1 It appears that, in reviewing the article, the authors did not present comparison data for the 2 postintervention phases showing a significant sustained compliance in relation to baseline. Maryanne McGuckin, Dr. ScEd., MT (ASCP) Senior Research Investigator, Adjunct Associate Professor, University of Pennsylvania School of Medicine Philadelphia, PA
E-mail: [email protected]
Reference
Reference
1. Leonard MK, Osterholt D, Kourbatova EV, Del Rio C, Wang W, Blumberg HM. How many sputum specimens are necessary to diagnose pulmonary tuberculosis? Am J Infect Control 2005;33:58-61.
1. McGuckin M, Taylor A, Martin V, Porten L, Salcido R. Evaluation of a patient education model for increasing hand hygiene compliance in an inpatient rehabilitation unit. Am J Infect Control 2004;32:235-8.
doi:10.1016/j.ajic.2006.01.006
doi:10.1016/j.ajic.2005.11.011
letters to the Editor
Vol. 34 No. 5
Re: How many sputum specimens are necessary to diagnose pulmonary tuberculosis To the Editor: We published the results of our study conducted at Grady Memorial Hospital (GMH), an urban universityaffiliated public hospital in Atlanta, Georgia, in an article by Leonard et al1 in your journal. The study evaluated sensitivity of acid-fast bacilli (AFB) smears to determine the optimal number of AFB sputum or respiratory specimens necessary to diagnose pulmonary tuberculosis (TB). In our study, we found that, in our institution, 2 respiratory specimens were adequate in establishing a diagnosis of pulmonary TB and that the third specimen added little additional diagnostic value. We received questions from readers regarding the sensitivity of AFB culture. We conducted a follow-up study with the same data with the purpose of determining the diagnostic yield of culture from each sputum specimen. All patients included in the previous reported study in the AJIC1 had 1 or more positive cultures for Mycobacterium tuberculosis recovered from sputum or respiratory specimens between January 1, 1997, and October 1, 2000. During the study period, 425 patients were diagnosed with pulmonary tuberculosis. Complete data on culture results were available on the 409 patients included in our analysis of AFB culture sensitivity. Cultures were performed on 918 respiratory specimens from these 409 patients. A total of 804 (88%) of 918 respiratory specimens were culture positive. Sensitivities of first, second, and third AFB cultures were calculated overall and separately for HIV-seronegative and HIV-seropositive patients. Proportions were compared using the Mantel-Haenszel x2 test and Fisher exact test as appropriate, and the Mantel-Haenszel odds ratios (OR) and corresponding 95% confidence intervals (CI) were calculated.
The overall sensitivity of a positive culture among patients with culture-confirmed tuberculosis increased from 91% with 1 sputum specimen to 98% and 100% with second and third sputum specimens collected, respectively. The sensitivity of the culture for HIVseronegative patients (94%, 99%, and 100% with 1, 2, and 3 smears collected) compared with that for HIV-infected patients (86%, 97%, and 100%, respectively, for 1, 2 and 3 smears collected) is shown in Table 1. The first culture was statistically significantly more sensitive in HIV-seronegative patients compared with HIV-infected patients (P 5 004), but the second culture was not (P 5 14). Pulmonary tuberculosis was diagnosed by the third positive culture when the first and second cultures were negative in 9 of 409 patients (2%) overall: 2 of 228 (1%) in HIV-seronegative patients, 4 of 138 (3%) in HIV-seropositive patients, and 3 of 43 (7%) in patients with unknown HIV status. In 122 of 409 (30%) patients, the first AFB sputum smear was negative, whereas the first culture was positive; in 1 of 409 (0.2%) patients, the first AFB sputum smear was positive, whereas the first AFB culture was negative. A total of 37 (9%) of 409 patients had a negative AFB culture from the first respiratory specimen. We analyzed predictors of needing more than 1 sputum culture for diagnosing pulmonary tuberculosis. Patients with a first positive AFB culture and patients with a first negative AFB culture had similar demographic characteristics. HIV-infected patients with pulmonary TB were more likely to have the first specimen be AFB culture negative compared with HIV-seronegative patients (20/138 [15%] vs 13/228 [6%], respectively; OR, 2.80; 95% CI: 1.35-5.84). Chest roentgenograms results were available for 393 patients. Having a roentgenogram with signs of upper or middle lobe infiltrate (OR, 0.17, 95% CI: 0.06-0.48) or cavitary lesion (OR, 0.04; 95% CI: 0.010.38) was negatively associated with having a first
Table 1. Analysis of sensitivity of acid-fast bacilli cultures from respiratory specimens in patients with culture confirmed pulmonary TB*y Overallz N = 409
HIV negative N = 228
HIV positive N = 138
Culture
Sensitivity, % (95% CI)
Additional benefit in sensitivity, % (95% CI)
Sensitivity, % (95% CI)
Additional benefit in sensitivity, % (95% CI)
Sensitivity, % (95% CI)
Additional benefit in sensitivity, % (95% CI)
1 2 3
91 (88-94) 98 (96-99) 100 (99-100)
7 (5-10) 2 (1-4)
94 (90-97) 99 (97-100) 100 (98-100)
5 (2-8) 1 (0.1-3)
86 (79-91) 97 (93-99) 100 (97-100)
11 (7-18) 3 (1-7)
*Additional benefit of second culture is in comparison with first culture, and additional benefit of third culture is in comparison with second culture. y Exact test was used for calculation of 95% confidence intervals for proportions. z Overall category includes 43 HIV-unknown patients.
letters to the Editor
June 2006
negative AFB culture from a respiratory specimen in univariate analysis (patients with normal roentgenogram were the referent group). In summary, as we found for our analysis of AFB smear,1 the third specimen for AFB culture from a respiratory specimen added little additional diagnostic value in establishing a diagnosis of pulmonary tuberculosis. The overall benefit in sensitivity of the third specimen was 2%, and there was a slightly higher diagnostic value among HIV-infected patients (additional benefit in sensitivity of 3%); the difference among HIV infected and HIV seronegative was statistically significant for the first, but not the second culture. Because our follow-up study was based only on culture-positive cases, we were unable to calculate specificity or negative predictive value for AFB culture. At our institution, 2 specimens proved to be adequate in almost all patients in establishing a diagnosis of pulmonary tuberculosis, and the benefit of the third specimen was of little diagnostic value. Other institutions should evaluate their data because considerable cost savings could be incurred by requiring 2 rather than 3 specimens to evaluate a patient for pulmonary TB. Michael K. Leonard, Jr, MD Ekaterina Kourbatova, MD Henry M. Blumberg, MD Assistant Professor of Medicine Divsion of Infectious Diseases Emory University School of Medicine
329
Reduction in nosocomial infection with improved hand hygiene in intensive care units of a tertiary care hospital in Argentina To the Editor: I wish to bring to your readers’ attention a misinterpretation of results reported in the Discussion section of the article by Rosenthal et al, Reduction in nosocomial infection with improved hand hygiene in intensive care units of a tertiary care hospital in Argentina. Am J Infect Control 2005;33:392-7. The authors’ discussion of our results for increasing hand hygiene compliance through patient empowerment (Partners In Your Care) was incorrectly reported. The objective of the reported study was to determine 2 postintervention phases: (1) no intervention and (2) visual reminder/ no patient empowerment. The study objective was to determine overall sustained compliance from baseline following the 2 postintervention phases. Based on this design, our findings showed an overall sustained increase in compliance of 56% from baseline (P < 001).1 It appears that, in reviewing the article, the authors did not present comparison data for the 2 postintervention phases showing a significant sustained compliance in relation to baseline. Maryanne McGuckin, Dr. ScEd., MT (ASCP) Senior Research Investigator, Adjunct Associate Professor, University of Pennsylvania School of Medicine Philadelphia, PA
E-mail: [email protected]
Reference
Reference
1. Leonard MK, Osterholt D, Kourbatova EV, Del Rio C, Wang W, Blumberg HM. How many sputum specimens are necessary to diagnose pulmonary tuberculosis? Am J Infect Control 2005;33:58-61.
1. McGuckin M, Taylor A, Martin V, Porten L, Salcido R. Evaluation of a patient education model for increasing hand hygiene compliance in an inpatient rehabilitation unit. Am J Infect Control 2004;32:235-8.
doi:10.1016/j.ajic.2006.01.006
doi:10.1016/j.ajic.2005.11.011