- Email: [email protected]
QuantiFERON®-TB Gold test for healthcare workers
Letters to the Editor
91
5. Clark CG. Do detergent residues damage the gut? Lancet 1984;2(8401):525. 6. Jonas G, Mahoney A, Murray J, Gertler S. Chemical colitis due to endoscope cleaning solutions. A mimic of pseudomembranous colitis. Gastroenterology 1988;95: 1403e1408. 7. Price E, Awad el-Kariem FM, Hately P, Harvey J, Gilkes J, Kempley S. Possible hazards of hypochlorite disinfection for feeding equipment for premature infants. J Hosp Infect 2006;67:90e92. 8. Fawley WN, Underwood S, Freeman J, et al. Efficacy of hospital cleaning agents and germicides against epidemic Clostridium difficile strains. Infect Control Hosp Epidemiol 2007;28:920e925.
E.H. Pricea,* G. Ayliffeb a Department of Medical Microbiology, Royal London Hospital, London, UK b Birmingham, UK E-mail address: elizabeth.price@ bartsandthelondon.nhs.uk Available online 10 March 2008 * Corresponding author. Address: Royal London Hospital, Medical Microbiology, Pathology & Pharmacy Building, London E1 2ES, UK.
ª 2008 The Hospital Infection Society. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.jhin.2008.01.009
QuantiFERON-TB Gold test for healthcare workers
Madam, We have read with interest the review focusing on the risk of nosocomial acquisition of tuberculosis (TB) by healthcare workers (HCWs).1 The author discussed measures for prevention and control of nosocomial TB transmission and emphasised the need for new tools to face the problem of latent TB infection (LTBI) identification among bacillus CalmetteeGue ´rin (BCG)-vaccinated HCWs. Tuberculin skin testing (TST) with protein-purified derivative (PPD) is associated with false-positive results due to (i) previous BCG vaccination or infection with other mycobacteria, (ii) booster phenomena secondary to remote mycobacterial infection or repeated testing and (iii) variability in its application and reading.2,3
QuantiFERON-TB Gold (QTBG) is a new test that detects g-interferon production in whole blood after stimulation with more specific but not exclusive antigens of Mycobacterium tuberculosis (MTB): ESAT-6, CFP-10 and TB 7.7 (Cellestis Ltd, Carnegie, Victoria, Australia). We compared QTBG test (in-tube method) to TST for the identification of LTBI among HCWs at the Institute of Infectious and Tropical Diseases of Brescia, Italy, where w200 patients with pulmonary TB were treated in the last five years. During February 2007, HCWs employed at the infectious diseases wards, and those from the TB outpatient clinic who had entered the regular TST screening programme at least 12 months earlier, were offered enrolment in the comparative study. Information on previous TST results and BCG vaccination status was retrieved from the hospital records. After written informed consent, HCWs with a previously negative TST result (skin induration <10 mm) were submitted to TST with 5 IU of PPD-S by the Mantoux method (reading at 72 h). TST conversion was defined as an increase of 10 mm in the diameter of skin induration compared to the previous TST result.4 At the same time of TST application a sample of blood was drawn for QTBG testing from these HCWs and from those with a previously positive TST test. HCWs with a positive TST had a chest X-ray done to exclude active pulmonary TB. The agreement between TST and QTBG test was measured by Kappa statistics. Of the 82 eligible staff, 65 (79.3%) HCWs were enrolled in the study; 45 (69%) were nurses or nursing assistants, 20 (31%) were physicians; 40 (61.5%) were females. Fifty-five (85%) HCWs reported that they had been vaccinated with BCG at job recruitment and 50 (77%) had been screened with TST at least once during their professional lives. No case of active TB was identified. Twentysix HCWs (40%) had had a previous positive TST and were not retested. Among 39 TST-negative HCWs, seven (18%) were TST positive in February 2007 (TST 10 mm) but none reached the criterion for TST conversion. Globally, 33 HCWs (51%) had a TST 10 mm; 58% (26/45) of nurses and 20% (7/35) of physicians had a positive TST (P ¼ 0.11). The QTBG test was positive in 18 HCWs (28%); the total agreement between TST and QTBG test was 52% for a Kappa coefficient of 0.05 (Table I). No statistically significant association between QTBG-positive result and gender, professional category or BCG status was found. Nurses had discordant results more frequently than physicians (81% vs 19%; P ¼ 0.07). In our study the agreement between the two tests was low and the prevalence of LTBI in HCWs identified by TST was higher than by QTBG test (51%
92
Letters to the Editor
Table I Agreement between tuberculin skin testing (TST) and QuantiFERON-TB Gold (QTBG) test results among healthcare workers N (%) Total agreement Agreement for TST >10 mm Agreement for TST <10 mm Kappa coefficient
34/65 (52) 10/33 (30) 24/32 (75) 0.05
vs 28%, respectively). The interpretation of TST results was probably confounded by serial TST and previous BCG vaccination with the possibility of false positive results secondary to cross-reaction with BCG or booster phenomenon. In fact, seven HCWs (18%) had skin induration to PPD 10 mm but did not reach the criterion for recent LTBI and therefore therapy of LTBI was not recommended. From these seven HCWs, only two (29%) resulted positive for QTBG test. We tested HCWs with QTBG test only once; thus we were unable to identify recent MTB infection by serial g-interferon measurement in previously QTBG-negative HCWs. Prospective studies of larger samples with QTBG test should help to define the criterion for QuantiFERON conversion and reversion and the incidence of booster phenomenon of QTBG induced by previous TST, allowing a better understanding of the potential role of QTBG in the screening of HCWs exposed to nosocomial risk of TB infection.5,6
6. Igari H, Watanabe A, Sato T. Booster phenomenon of QuantiFERON-TB Gold after prior intradermal PPD injection. Int J Tuberc Lung Dis 2007;11:788e791.
A.C. Carvalhoa N. Crottib M. Crippac R. Basche `a G. De Iacoa S. Signorinia L. Jacquotb G. Cristinid F. Castellia G. Carosia A. Matteellia,* a Institute of Infectious and Tropical Diseases, University of Brescia, Italy b Health Management Service, Spedali Civili, Brescia, Italy c Occupational Health Institute, Spedali Civili, Brescia, Italy d Division of Infectious Diseases, Spedali Civili, BS, Italy E-mail address: [email protected] Available online 21 March 2008 * Corresponding author. Address: Institute of Infectious and Tropical Diseases, University of Brescia, Piazza Spedali Civili, 1, 25125 Brescia, Italy. Tel.: þ39 030 3995802; fax: þ39 030 303061. ª 2008 The Hospital Infection Society. Published by Elsevier Ltd. All rights reserved.
Conflict of interest statement None declared.
doi:10.1016/j.jhin.2008.01.032
Funding sources None.
Healthcare workers’ knowledge of the carriage of meticillin-resistant Staphylococcus aureus by patients: the first step in controlling spread
References 1. Humphreys H. Control and prevention of healthcare-associated tuberculosis: the role of respiratory isolation and personal respiratory protection. J Hosp Infect 2007;66:1e5. 2. Menzies D. Interpretation of repeated tuberculin tests. Boosting, conversion, and reversion. Am J Respir Crit Care Med 1999;159:15e21. 3. Wang L, Turner MO, Elwood RK, Schulzer M, FitzGerald JM. A meta-analysis of the effect of Bacille Calmette Gue ´rin vaccination on tuberculin skin test measurements. Thorax 2002; 57:804e809. 4. American Thoracic Society (ATS) and Centers for Disease Control. Targeted tuberculin testing and treatment of latent tuberculosis infection. Am J Respir Crit Care Med 2000;161: S221eS247. 5. Pai M, Joshi R, Dogra S, et al. Serial testing of health care workers for tuberculosis using interferon-gamma assay. Am J Respir Crit Care Med 2006;174:349e355.
Madam, In France, the level of meticillin-resistant Staphylococcus aureus (MRSA) cases is one of the highest among European countries.1,2 A national programme for limiting spread of MRSA in French hospitals was implemented in 1999. This programme was based on identification and notification of patients’ MRSA carriage and the implementation of isolation precautions.3 The first step in implementing appropriate precautions is to ensure that healthcare workers (HCWs) are aware of their patients’ status. We therefore decided to assess the knowledge of HCWs of MRSA carriage by the patients in our hospital.
91
5. Clark CG. Do detergent residues damage the gut? Lancet 1984;2(8401):525. 6. Jonas G, Mahoney A, Murray J, Gertler S. Chemical colitis due to endoscope cleaning solutions. A mimic of pseudomembranous colitis. Gastroenterology 1988;95: 1403e1408. 7. Price E, Awad el-Kariem FM, Hately P, Harvey J, Gilkes J, Kempley S. Possible hazards of hypochlorite disinfection for feeding equipment for premature infants. J Hosp Infect 2006;67:90e92. 8. Fawley WN, Underwood S, Freeman J, et al. Efficacy of hospital cleaning agents and germicides against epidemic Clostridium difficile strains. Infect Control Hosp Epidemiol 2007;28:920e925.
E.H. Pricea,* G. Ayliffeb a Department of Medical Microbiology, Royal London Hospital, London, UK b Birmingham, UK E-mail address: elizabeth.price@ bartsandthelondon.nhs.uk Available online 10 March 2008 * Corresponding author. Address: Royal London Hospital, Medical Microbiology, Pathology & Pharmacy Building, London E1 2ES, UK.
ª 2008 The Hospital Infection Society. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.jhin.2008.01.009
QuantiFERON-TB Gold test for healthcare workers
Madam, We have read with interest the review focusing on the risk of nosocomial acquisition of tuberculosis (TB) by healthcare workers (HCWs).1 The author discussed measures for prevention and control of nosocomial TB transmission and emphasised the need for new tools to face the problem of latent TB infection (LTBI) identification among bacillus CalmetteeGue ´rin (BCG)-vaccinated HCWs. Tuberculin skin testing (TST) with protein-purified derivative (PPD) is associated with false-positive results due to (i) previous BCG vaccination or infection with other mycobacteria, (ii) booster phenomena secondary to remote mycobacterial infection or repeated testing and (iii) variability in its application and reading.2,3
QuantiFERON-TB Gold (QTBG) is a new test that detects g-interferon production in whole blood after stimulation with more specific but not exclusive antigens of Mycobacterium tuberculosis (MTB): ESAT-6, CFP-10 and TB 7.7 (Cellestis Ltd, Carnegie, Victoria, Australia). We compared QTBG test (in-tube method) to TST for the identification of LTBI among HCWs at the Institute of Infectious and Tropical Diseases of Brescia, Italy, where w200 patients with pulmonary TB were treated in the last five years. During February 2007, HCWs employed at the infectious diseases wards, and those from the TB outpatient clinic who had entered the regular TST screening programme at least 12 months earlier, were offered enrolment in the comparative study. Information on previous TST results and BCG vaccination status was retrieved from the hospital records. After written informed consent, HCWs with a previously negative TST result (skin induration <10 mm) were submitted to TST with 5 IU of PPD-S by the Mantoux method (reading at 72 h). TST conversion was defined as an increase of 10 mm in the diameter of skin induration compared to the previous TST result.4 At the same time of TST application a sample of blood was drawn for QTBG testing from these HCWs and from those with a previously positive TST test. HCWs with a positive TST had a chest X-ray done to exclude active pulmonary TB. The agreement between TST and QTBG test was measured by Kappa statistics. Of the 82 eligible staff, 65 (79.3%) HCWs were enrolled in the study; 45 (69%) were nurses or nursing assistants, 20 (31%) were physicians; 40 (61.5%) were females. Fifty-five (85%) HCWs reported that they had been vaccinated with BCG at job recruitment and 50 (77%) had been screened with TST at least once during their professional lives. No case of active TB was identified. Twentysix HCWs (40%) had had a previous positive TST and were not retested. Among 39 TST-negative HCWs, seven (18%) were TST positive in February 2007 (TST 10 mm) but none reached the criterion for TST conversion. Globally, 33 HCWs (51%) had a TST 10 mm; 58% (26/45) of nurses and 20% (7/35) of physicians had a positive TST (P ¼ 0.11). The QTBG test was positive in 18 HCWs (28%); the total agreement between TST and QTBG test was 52% for a Kappa coefficient of 0.05 (Table I). No statistically significant association between QTBG-positive result and gender, professional category or BCG status was found. Nurses had discordant results more frequently than physicians (81% vs 19%; P ¼ 0.07). In our study the agreement between the two tests was low and the prevalence of LTBI in HCWs identified by TST was higher than by QTBG test (51%
92
Letters to the Editor
Table I Agreement between tuberculin skin testing (TST) and QuantiFERON-TB Gold (QTBG) test results among healthcare workers N (%) Total agreement Agreement for TST >10 mm Agreement for TST <10 mm Kappa coefficient
34/65 (52) 10/33 (30) 24/32 (75) 0.05
vs 28%, respectively). The interpretation of TST results was probably confounded by serial TST and previous BCG vaccination with the possibility of false positive results secondary to cross-reaction with BCG or booster phenomenon. In fact, seven HCWs (18%) had skin induration to PPD 10 mm but did not reach the criterion for recent LTBI and therefore therapy of LTBI was not recommended. From these seven HCWs, only two (29%) resulted positive for QTBG test. We tested HCWs with QTBG test only once; thus we were unable to identify recent MTB infection by serial g-interferon measurement in previously QTBG-negative HCWs. Prospective studies of larger samples with QTBG test should help to define the criterion for QuantiFERON conversion and reversion and the incidence of booster phenomenon of QTBG induced by previous TST, allowing a better understanding of the potential role of QTBG in the screening of HCWs exposed to nosocomial risk of TB infection.5,6
6. Igari H, Watanabe A, Sato T. Booster phenomenon of QuantiFERON-TB Gold after prior intradermal PPD injection. Int J Tuberc Lung Dis 2007;11:788e791.
A.C. Carvalhoa N. Crottib M. Crippac R. Basche `a G. De Iacoa S. Signorinia L. Jacquotb G. Cristinid F. Castellia G. Carosia A. Matteellia,* a Institute of Infectious and Tropical Diseases, University of Brescia, Italy b Health Management Service, Spedali Civili, Brescia, Italy c Occupational Health Institute, Spedali Civili, Brescia, Italy d Division of Infectious Diseases, Spedali Civili, BS, Italy E-mail address: [email protected] Available online 21 March 2008 * Corresponding author. Address: Institute of Infectious and Tropical Diseases, University of Brescia, Piazza Spedali Civili, 1, 25125 Brescia, Italy. Tel.: þ39 030 3995802; fax: þ39 030 303061. ª 2008 The Hospital Infection Society. Published by Elsevier Ltd. All rights reserved.
Conflict of interest statement None declared.
doi:10.1016/j.jhin.2008.01.032
Funding sources None.
Healthcare workers’ knowledge of the carriage of meticillin-resistant Staphylococcus aureus by patients: the first step in controlling spread
References 1. Humphreys H. Control and prevention of healthcare-associated tuberculosis: the role of respiratory isolation and personal respiratory protection. J Hosp Infect 2007;66:1e5. 2. Menzies D. Interpretation of repeated tuberculin tests. Boosting, conversion, and reversion. Am J Respir Crit Care Med 1999;159:15e21. 3. Wang L, Turner MO, Elwood RK, Schulzer M, FitzGerald JM. A meta-analysis of the effect of Bacille Calmette Gue ´rin vaccination on tuberculin skin test measurements. Thorax 2002; 57:804e809. 4. American Thoracic Society (ATS) and Centers for Disease Control. Targeted tuberculin testing and treatment of latent tuberculosis infection. Am J Respir Crit Care Med 2000;161: S221eS247. 5. Pai M, Joshi R, Dogra S, et al. Serial testing of health care workers for tuberculosis using interferon-gamma assay. Am J Respir Crit Care Med 2006;174:349e355.
Madam, In France, the level of meticillin-resistant Staphylococcus aureus (MRSA) cases is one of the highest among European countries.1,2 A national programme for limiting spread of MRSA in French hospitals was implemented in 1999. This programme was based on identification and notification of patients’ MRSA carriage and the implementation of isolation precautions.3 The first step in implementing appropriate precautions is to ensure that healthcare workers (HCWs) are aware of their patients’ status. We therefore decided to assess the knowledge of HCWs of MRSA carriage by the patients in our hospital.