Skin Test Conversion Rates Research Articles

Reduction in Tuberculin Skin-Test Conversions among Medical House Staff Associated with Improved Tuberculosis Infection Control Practices

To assess the efficacy of an infection control program as measured by tuberculin skin-test (TST) conversion rates in medical house staff.Observational study.University-based hospital in New York City serving a large indigent population.Medical house staff.TST conversions were measured every 6 months in medical house staff from June 1992 to June 1994. Compliance with the isolation policy was measured by identifying room locations 24 hours after admission of patients who had Mycobacterium tuberculosis recovered from respiratory specimens.The TST conversion rate decreased from 5.8 to 0, 2.3, and 0 per 100 person years of exposure in successive 6-month periods. The estimated annual TST conversion rate among interns fell from 7 per 100 person years in June 1992 to 0 per 100 person years in June 1993 and 0 per 100 person years in June 1994 (P < .029). The proportion of patients with pulmonary tuberculosis who were isolated in negative-pressure rooms increased from 38% to 75% over the study period (P < .01).Development of a multifaceted infection control program can decrease the risk of nosocomial tuberculosis infection in medical house staff.

Reduction in tuberculin skin-test conversions among medical house staff associated with improved tuberculosis infection control practices.

To assess the efficacy of an infection control program as measured by tuberculin skin-test (TST) conversion rates in medical house staff. Observational study. University-based hospital in New York City serving a large indigent population. Medical house staff. TST conversions were measured every 6 months in medical house staff from June 1992 to June 1994. Compliance with the isolation policy was measured by identifying room locations 24 hours after admission of patients who had Mycobacterium tuberculosis recovered from respiratory specimens. The TST conversion rate decreased from 5.8 to 0, 2.3, and 0 per 100 person years of exposure in successive 6-month periods. The estimated annual TST conversion rate among interns fell from 7 per 100 person years in June 1992 to 0 per 100 person years in June 1993 and 0 per 100 person years in June 1994 (P < .029). The proportion of patients with pulmonary tuberculosis who were isolated in negative-pressure rooms increased from 38% to 75% over the study period (P < .01). Development of a multifaceted infection control program can decrease the risk of nosocomial tuberculosis infection in medical house staff.

Reduction in tuberculin skin-test conversion rate after improved adherence to tuberculosis isolation.

The rate of purified protein derivative (PPD) conversion in workers at our hospital increased to 1.7% in 1991. After implementation of mandatory respiratory isolation of patients with community-acquired pneumonia, the rate dropped to 0.6%. This policy may protect workers in institutions where the majority of patients with pneumonia have risk factors for tuberculosis.

Varied approaches to tuberculosis control in a multihospital system.

To document the actual tuberculosis (TB) control policies and procedures in a nonoutbreak setting in a variety of hospitals. To determine if any particular practices are linked to higher rates of employee tuberculin skin-test conversion. Survey of hospital occupational health and infection control practitioners for the year 1994 regarding hospital TB policies. Review of hospital records to verify the number of patients with TB at each hospital and to verify the number of employees with positive tuberculin skin tests. Smoke-stick testing of negative-pressure ventilation rooms. A 13-hospital health system in the Midwest. Hospitals ranged in size from 40 to 1,208 beds (median 220) and employed 150 to 6,500 workers (median 875). There were seven rural and six urban centers, including four teaching hospitals. All 13 hospitals had TB control plans, and all performed annual tuberculin skin testing on employees. Annual skin-test positivity rates ranged from 0% to 1.0% (median 0.3%). Negative-pressure ventilation rooms were available in 11 hospitals. The percentage of negative-pressure rooms with effective negative pressure ranged from 44% to 100% (median 95%). Three of the 13 hospitals used high-efficiency particulate air (HEPA) masks as primary personal respiratory protection, and 8 used dust-mist or dust-mist-fume masks. We found no relation between the type of face mask used, number of functional negative-pressure rooms, or hospital TB risk category, and employee skin-test conversion rates. Considerable variation existed in the TB control policies and procedures between hospitals, but employee TB skin-test conversion rates were low in all settings.

Reduction in Tuberculin Skin-Test Conversion Rate after Improved Adherence to Tuberculosis Isolation

The rate of purified protein derivative (PPD) conversion in workers at our hospital increased to 1.7% in 1991. After implementation of mandatory respiratory isolation of patients with community-acquired pneumonia, the rate dropped to 0.6%. This policy may protect workers in institutions where the majority of patients with pneumonia have risk factors for tuberculosis.

Dramatic decrease in tuberculin skin test conversion rate among employees at a hospital in New York City

Background: The Centers for Disease Control and Prevention recently issued updated guidelines for preventing the transmission of tuberculosis in health care facilities. Many recommendations, including the use of high-efficiency particulate air filter respirators, are expensive to implement and of unproven efficacy. We therefore reviewed the tuberculin skin test conversion rate among our employees from 1991 to 1993, before introduction of high-efficiency particulate air filter respirators. During this period, several other improvements in tuberculosis control were implemented. Methods: Employee tuberculin test conversion rates were reviewed by 6-month interval from 1991 to 1993. Results: Throughout the study period, several tuberculosis control measures were implemented, including early isolation of patients with suspected cases of tuberculosis in rooms with negative-pressure ventilation, placement of germicidal UV light fixtures into patient rooms and common areas, and use of Technol shields (Technol, Inc., Fort Worth, Texas) (1991), particulate respirators (1992), and dust-mist-fume respirators (1993). With these improvements, the conversion rate among employees fell from 20.7% in the first 6 months of 1991 to 5.8% in the latter half of 1993. Conclusions: The rate of skin test conversion among our employees decreased before introduction of high-efficiency particulate air filter respirators. This suggests that nosocomial spread of tuberculosis can be decreased by means of previously established, less costly methods.

Preventing the nosocomial transmission of tuberculosis.

To study the efficacy of expanded tuberculosis infection control measures consisting primarily of administrative controls. Descriptive case series. University-affiliated, inner-city hospital. Introduction of expanded tuberculosis infection control measures (including an expanded respiratory isolation policy). The number of tuberculosis exposure episodes and skin test conversion rates of health care workers were measured before and after implementation of expanded infection control measures. Tuberculosis exposure episodes (the number of patients who were not placed in respiratory isolation at admission but who subsequently had a diagnosis of acid-fast bacilli smear-positive pulmonary tuberculosis during that admission or within 2 weeks of discharge) were compared for two time periods: the 8 months before and the 28 months after implementation of infection control measures. Tuberculin skin test conversion rates among health care workers were evaluated during a 2.5-year period. After expanded infection control measures were implemented, the number of tuberculosis exposure episodes decreased from 4.4 per month (35 episodes among 103 patient admissions for potentially infectious tuberculosis over 8 months) to 0.6 per month (18 episodes among 358 patient admissions for smear-positive pulmonary tuberculosis over 28 months) (odds ratio, 9.72; 95% CI, 4.99 to 19.25 [P < 0.001]). The cumulative number of days per month that potentially infectious patients with tuberculosis were not in isolation decreased from 35.4 to 3.3 (P < 0.001). A concomitant decrease in tuberculin skin test conversion rates in health care workers was seen; 6-month tuberculin skin test conversion rates decreased steadily from 3.3% (118 conversions in 3579 health care workers; 1/92 to 6/92), 1.7%, 1.4%, 0.6%, to 0.4% (23 conversions in 5153 workers [1/94 to 6/94]) (P < 0.001). Infection control measures effectively prevented nosocomial transmission of tuberculosis to health care workers. Administrative controls appear to be the most important component of a tuberculosis infection control program and should be the first focus of such a program, especially at public hospitals, where resources are most likely to be limited.

SHEA-CDC TB Survey, Part II: Efficacy of TB Infection Control Programs at Member Hospitals, 1992

AbstractObjective:To assess the efficacy of current Myco-bacterium tuberculosis control measures.Design:Voluntary questionnaire to members of the Society for Healthcare Epidemiology of America.Results:Healthcare worker (HCW) tuberculin skin-test (TST) conversion rates were significantly higher in larger hospitals ( ≥ 437 beds) (0.9% versus 0.6%; P &lt; 0.05), or in hospitals reporting ≥ 6 TB patients in 1992 (1.2% versus 0.6%; P &lt; 0.05). Among larger hospitals or those hospitals surveyed reporting ≥ 6 TB patients, those without at least three of the four criteria suggested in the 1990 Centers for Disease Control and Prevention (CDC) TB guidelines for acid-fast bacilli (AFB) isolation (specifically, a single-patient room; negative pressure; and air exhausted directly outside) had significantly higher annual TST conversion rates than those with these criteria (1.8% versus 0.6%; P &lt; 0.05). Respiratory therapist or bronchoscopist TST conversion rates were significantly lower in hospitals compliant with the exhaust criteria (1.2% versus 2.8%; P &lt; 0.05). Regardless of hospital characteristic, HCW TST conversion rates did not differ between hospitals in which HCWs used surgical masks or used disposable particulate respirators.Conclusion:Among larger hospitals or hospitals reporting ≥ 6 TB patients per year, failure to comply with the 1990 CDC TB recommendations for AFB isolation room guidelines was associated with higher HCW TST conversion rates. These data suggest that complete implementation of the 1990 CDC TB guidelines would decrease HCWs’ risk of nosocomial transmission of TB in larger hospitals or those reporting more TB patients. However, in nonoutbreak situations, disposable particulate respirators or submicron surgical masks may not offer significantly greater protection to HCWs than surgical masks.

Efficacy of control measures in preventing nosocomial transmission of multidrug-resistant tuberculosis to patients and health care workers.

To assess the efficacy of control measures in decreasing nosocomial transmission of multidrug-resistant tuberculosis. Retrospective cohort study. A teaching hospital in New York City. 40 patients hospitalized with multidrug-resistant tuberculosis (case-patients) and health care workers receiving tuberculin skin testing. Centers for Disease Control and Prevention (CDC) 1990 guidelines for preventing transmission of tuberculosis, including 1) prompt isolation and treatment of patients with tuberculosis; 2) rapid diagnostic techniques for processing Mycobacterium tuberculosis specimens; 3) negative-pressure isolation rooms; and 4) molded surgical masks for health care workers. Proportion of case-patients with nosocomially acquired tuberculosis and rate of tuberculin skin test conversion among health care workers before and after implementation of control measures. The proportion of patients with multidrug-resistant strains of M. tuberculosis decreased after the interventions (10 of 70 [14%] compared with 30 of 95 [32%] patients before the intervention; relative risk [RR], 0.5; 95% CI, 0.2 to 0.9). Before onset of multidrug-resistant tuberculosis, case-patients in the intervention period were as likely to be hospitalized on high-risk wards containing patients with tuberculosis (4 of 10 compared with 17 of 30 patients; RR, 0.7; P = 0.5) but were less likely to be exposed to another case-patient with tuberculosis (1 of 10 compared with 20 of 30 patients; RR, 0.2; P = 0.003). Tuberculin skin test conversion rates for health care workers assigned to wards housing patients with tuberculosis were lower in the intervention period than in the preintervention period (4 of 78 [5%] compared with 15 of 90 [17%] conversions; P = 0.02), decreasing to levels observed for workers assigned to other wards (4 of 78 [5%] compared with 9 of 228 [4%] conversions; P = 0.7). Implementing control measures reduced nosocomial transmission of multidrug-resistant strains to patients and health care workers.

The effect of the booster phenomenon on the tuberculin skin test conversion rate

The effect of the booster phenomenon on the tuberculin skin test conversion rate

Tuberculosis contact investigation: Two years of experience in New York City correctional facilities

Background: An increasing incidence of tuberculosis has been observed in the New York City correctional system. Methods: The diagnosis of active tuberculosis in persons within the correctional setting results in an investigation, with the identification and screening of contacts. Results: Thirty-four such investigations in the past 2 years in the New York City correctional system, where all inmates are screened for tuberculosis on admission, have resulted in an overall tuberculin skin test conversion rate of 6.74% in 1306 inmates. In 21 of these investigations the index had both smears and cultures positive for Mycobacterium tuberculosis and the conversion rate was 7.37% in 719 contacts tested. In seven investigations the index patient had a culture only positive for M. tuberculosis and the conversion rate was 6.58% in 243 inmates. In six investigations in which the index patients were subsequently found to have nontuberculous pneumonia or mycobacteria other than M. tuberculosis the conversion rate was 5.52% in 344 inmates. These rates are not statistically different. Conclusions: Whether the observed conversions in these events or in any of the contact investigations are due to intramural spread, anergy on admission, the booster phenomenon, or incubation of disease on admission is not known. The 5.5% conversion rate in those exposed to inmates confirmed not to have tuberculosis suggests the influence of booster phenomenon and consideration of two-step testing on admission.

Increased Rate of Tuberculin Skin Test Conversion Among Workers at a University Hospital

AbstractObjectives:To summarize the results of an investigation of increased rates of tuberculin skin test conversion in employees at a university hospital.Design:The results of annual tuberculin skin tests performed on all 1,845 hospital employees from 1986 to 1991 were reviewed.Setting:A 450-bed acute tertiary care university hospital.Results:The rate of tuberculin skin test conversion was 0.35% (standard deviation ± 0.15) from 1986 to 1989 and increased to 1.7% during 1991. Investigation revealed deviations from the Centers for Disease Control (CDC) guidelines for tuberculosis control, which included the failure to consider tuberculosis as a probable cause of community-acquired pneumonia and the failure to initiate isolation precautions when tuberculosis was suspected.Conclusions:The epidemic appeared to be secondary to delays in diagnosis and isolation of patients with pulmonary tuberculosis. Future control measures should include isolation of all hospital patients admitted with pneumonia until tuberculosis has been excluded.

Increased rate of tuberculin skin test conversion among workers at a university hospital.

To summarize the results of an investigation of increased rates of tuberculin skin test conversion in employees at a university hospital. The results of annual tuberculin skin tests performed on all 1,845 hospital employees from 1986 to 1991 were reviewed. A 450-bed acute tertiary care university hospital. The rate of tuberculin skin test conversion was 0.35% (standard deviation +/- 0.15) from 1986 to 1989 and increased to 1.7% during 1991. Investigation revealed deviations from the Centers for Disease Control (CDC) guidelines for tuberculosis control, which included the failure to consider tuberculosis as a probable cause of community-acquired pneumonia and the failure to initiate isolation precautions when tuberculosis was suspected. The epidemic appeared to be secondary to delays in diagnosis and isolation of patients with pulmonary tuberculosis. Future control measures should include isolation of all hospital patients admitted with pneumonia until tuberculosis has been excluded.

Hospital outbreak of multidrug-resistant Mycobacterium tuberculosis infections. Factors in transmission to staff and HIV-infected patients.

To describe transmission of multidrug-resistant (MDR) Mycobacterium tuberculosis infection among patients and health care workers (HCWs) in a ward and clinic for human immunodeficiency virus (HIV)-infected patients in a hospital, four studies were conducted. Case patients and control patients were persons who had been treated in the HIV ward or clinic, whose clinical course was consistent with tuberculosis and who had at least one positive culture for M tuberculosis between January 1, 1988, and January 31, 1990, resistant to at least isoniazid and rifampin (case patients), or whose isolates were susceptible to all drugs tested (control patients). In the first study, case patients and control patients were compared to identify risk factors for MDR tuberculosis. In the second study, inpatient and outpatient days of MDR tuberculosis case patients were compared to determine whether acid-fast bacillus (AFB) smear-positivity or aerosolized pentamidine use was associated with higher numbers of subsequent MDR tuberculosis cases among exposed patients. In the third study, restriction fragment length polymorphism analysis was performed on available MDR and sensitive M tuberculosis isolates. In the fourth study, skin test conversion rates among HCWs in the HIV ward and clinic were compared with those of HCWs in another ward, and the strength of the associations between skin test conversions among HCWs on the HIV ward and the number of person-days that AFB smear-positive case patients and control patients were on this ward was estimated. Case patients were more likely than control patients to have been exposed on the HIV ward or clinic to an AFB smear-positive case patient (P less than .001). Inpatient and outpatient days of MDR tuberculosis case patients were associated with more subsequent cases of MDR tuberculosis if exposing case patients were smear-positive or if they received aerosolized pentamidine (P less than or equal to .01). Of 13 MDR isolates, all had one of two restriction fragment length polymorphism patterns; 10 sensitive isolates had restriction fragment length polymorphism patterns that were different from each other. The HCW skin test conversion rate was higher on the HIV ward and clinic than on the comparison ward (P less than .01). The risk of occupational acquisition of infection increased in direct proportion to the number of person-days that AFB smear-positive case patients were on the HIV ward (r = .75; P = .005), but did not increase in proportion to the number of person-days that AFB smear-positive control patients were there (r = -.36; P = NS). After isolation measures for AFB smear-positive tuberculosis patients were improved, MDR tuberculosis cases decreased to seven of 214 tuberculosis patients. Nosocomial transmission of MDR M tuberculosis infection to patients and HCWs occurred on the HIV ward and clinic. Infectiousness of MDR tuberculosis case patients was associated with AFB sputum-smear positivity. Case patients with MDR tuberculosis created a greater risk of skin test conversion for HCWs on the HIV ward than drug-susceptible control patients.

Nosocomial transmission of multidrug-resistant Mycobacterium tuberculosis. A risk to patients and health care workers.

To determine the factors associated with the development of multidrug-resistant tuberculosis among patients at a New York City Hospital and to investigate possible nosocomial transmission. A retrospective case-control study and tuberculin skin test survey. Twenty-three patients with tuberculosis whose isolates were resistant to at least isoniazid and rifampin (case patients) were compared with patients with tuberculosis whose isolates were susceptible to all agents tested (controls). Tuberculin skin test conversion rates were compared among health care workers assigned to wards where patients with tuberculosis were frequently or rarely admitted. A large, teaching hospital in New York City. Mycobacterium tuberculosis isolates from case patients and controls were typed by restriction fragment length polymorphism analysis. Case patients were younger (median age, 34 compared with 42 years; P = 0.006), more likely to be seropositive for HIV (21 of 23 compared with 11 of 23 patients; odds ratio, 11.5; 95% CI, 1.9 to 117), and more likely to have had a previous hospital admission within 7 months before the onset of tuberculosis (19 of 23 compared with 5 of 23 patients; odds ratio, 17.1; CI, 3.3 to 97), particularly on one ward (12 of 23 compared with 0 of 23 patients; odds ratio, undefined; P = 0.002). Health care workers assigned to wards housing case patients were more likely to have tuberculin skin test conversions than were health care workers assigned to other wards (11 of 32 compared with 1 of 47 health care workers; P less than 0.001). Few (6 of 23) case patients were placed in acid-fast bacilli isolation, and no rooms tested had negative pressure. Of 16 available multidrug-resistant isolates obtained from case patients, 14 had identical banding patterns by restriction fragment length polymorphism analysis. In contrast, M. tuberculosis isolates from controls with drug-susceptible tuberculosis had patterns distinct from each other and from those of case patients. These data suggest nosocomial transmission of multidrug-resistant tuberculosis occurred from patient to patient and from patient to health care worker and underscore the need for effective acid-fast bacilli isolation facilities and adherence to published infection control guidelines in health care institutions.

Tuberculosis screening in the long-term care setting.

Tuberculosis (TB) skin-testing practices in long-term care facilities (LTCFs) in North Carolina (NC) were assessed from a 56% (148/263) response to a comprehensive TB screening questionnaire. TB skin tests were administered to employees on initial employment by 98% and annually by 97% of the LTCFs, generally (74%) by the Mantoux method. Employee skin tests were read at the appropriate time interval of 48 to 72 hours by 91%, but less than half used diameter of induration when interpreting reactive tests. The booster test was performed on new employees at eight (6%) of the LTCFs. TB skin tests were routinely performed on newly admitted residents by 56% or conditionally required by 18%, generally (73%) by the Mantoux method. Resident skin tests were read at the appropriate time interval of 48 to 72 hours by 92%, but again only half correctly interpreted reactive tests as significant. Residents received routine annual skin tests at 71% of the LTCFs, generally (80%) by the Mantoux method. Eight (6%) facilities routinely performed the booster test on newly admitted residents. TB infection prevalence in new employees during 1983 was 8.1% (47/578) in seven LTCFs and in newly admitted residents was 6.4% (7/110) in three LTCFs supplying this data. The five-year mean TB skin test conversion rate among employees was 1.1% (101/9545) in 12 LTCFs and among residents was 0.9% (46/5216) in nine LTCFs supplying this data. Lack of compliance to established TB skin-testing guidelines in NC LTCF was prevalent. In recognition of described endemic and epidemic spread of TB in LTCFs, residents and employees of LTCFs should be screened for TB utilizing established skin-testing practices.

Nosocomial tuberculosis.

Hospital employees are at risk of contracting tuberculosis from patients. The undiagnosed case with sputum-smear positive for acid-fast bacilli is the usual source case. However, even the smear-negative patient may pose a risk. This was documented by a high rate of skin test conversion in hospital staff exposed to a smear-negative, culture-positive patient in a respiratory intensive care unit. The patient required bronchoscopy, intubation, and assisted ventilation. Of susceptible hospital staff members who were exposed to the index case, 14 of 45 (31%) converted their PPD skin test. Ten of 13 (77%) susceptible hospital staff members present at the time of bronchoscopy converted, compared with 4 of 32 (12.5%) who were not present at bronchoscopy (Fischer's exact test p = 0.0006). Rough calculations suggest that during the bronchoscopy and intubation the index case generated at least 249 infectious units per hour. At the ventilation levels in this area, this resulted in 1 infectious unit of tuberculosis in each 68.9 cubic feet of air. Improved ventilation, high efficiency filters, and ultraviolet irradiation are effective recommended ways to clean the air of infectious particles.

Tuberculosis Transmission in a Large Urban Jail

Following diagnosis of moderately advanced tuberculosis in an inmate of Cook County Jail, tuberculin testing was performed to assess the degree of transmission of tuberculosis within the jail. Twenty-three percent of inmates exposed to the index patient were initially found to be tuberculin positive. Subsequent tuberculin testing three months later demonstrated a 71% rate of skin-test conversion in previously tuberculin-negative inmates exposed to the index patient. The rate of infectivity of tuberculosis within a jail is analogous to a household situation. Despite major obstacles, modern programs of tuberculosis screening and treatment are essential in correctional institutions.

Tuberculosis transmission in a large urban jail

Following diagnosis of moderately advanced tuberculosis in an inmate of Cook County Jail, tuberculin testing was performed to assess the degree of transmission of tuberculosis within the jail. Twenty-three percent of inmates exposed to the index patient were initially found to be tuberculin positive. Subsequent tuberculin testing three months later demonstrated a 71% rate of skin-test conversion in previously tuberculin-negative inmates exposed to the index patient. The rate of infectivity of tuberculosis within a jail is analogous to a household situation. Despite major obstacles, modern programs of tuberculosis screening and treatment are essential in correctional institutions. (<i>JAMA</i>237:791-792, 1977)