Skin Test Conversion Rates Research Articles

Erratum to `Tuberculosis risk in the biologic era: tuberculin skin test conversion rates in children with rheumatologic diseases` [Turk J Pediatr 2021; 63: 978-985

This article is corrected. DOI: 10.24953/turkjped.2021.06.005.

Tuberculosis Exposure and Conversion Rates Can Guide Deimplementation of Annual Tuberculosis Screening

Background: The CDC recently updated recommendations on tuberculosis (TB) screening in healthcare facilities, suggesting the discontinuation of annual TB screening. However, hospitals may opt to continue based on their local TB epidemiology. We assessed TB infection control parameters in our facility to guide the implementation of the new CDC recommendations. Methods:We retrieved data for patients with an International Classification of Disease, Tenth Revision (ICD-10) code for TB treated at the University of Iowa Hospitals and Clinics during 2016–2019. We supplemented our search with microbiology data: culture or PCR for Mycobacterium tuberculosis. Based on manual chart review, we adjudicated each patient as active TB, latent TB, previously treated TB, unclear history, or no TB. We further labeled active TB cases based on their risk of transmission (pulmonary or extrapulmonary cases that underwent an aerosol generating procedure). We then calculated the number of exposure events associated with those patients and tuberculin skin test (TST) conversion rates among the exposed. Results: During 2016–2019, we identified 197 patients based on ICD-10 codes. In total, 10 additional patients were detected by microbiology data review. Of these 207 patients, 48 (23.2%) had active TB: lung, n = 24 (50%); lymph node, n = 9 (19%); bone or spine, n = 5 (10%); eye, n = 3 (6%); disseminated, n = 2 (4%); pleura, n = 2 (4%); skin abscess, n = 2 (4%); and meningitis, n = 1 (2%). Of the 24 pulmonary patients, 6 (25%) had either a positive smear or a cavity on imaging. In total, 159 patients were excluded: no TB, n = 22 (14%); latent TB, n = 27 (17%); old or treated TB, n = 93 (58%); and unclear history, n = 9 (6%). Of the 48 cases with active TB, 31 (65%) were deemed potentially infectious. Also, 10 cases (32%) led to the exposure of 204 healthcare workers (HCWs). Baseline and postexposure TST were available for 179 HCWs (88%); 72 (35%) followed up in the employee health clinic within the 8–12 weeks after exposure. Of 161 HCWs with a negative TST at baseline, no conversions occurred. Of 18 HCWs with positive TST at baseline, no HCW developed symptoms during the observation period. Conclusions: Nearly one-third of infectious TB cases led to HCW exposures in a low-incidence setting. However, no TST conversions or active TB infections were seen. Exposure and conversion rates are useful indicators of TB infection control in healthcare facilities and may help guide implementation of the new CDC TB control recommendations.Funding: NoneDisclosures: None

Serial testing of healthcare workers for latent tuberculosis infection and long-term follow up for development of active tuberculosis.

BackgroundHealthcare workers (HCWs) are at high risk of tuberculosis (TB) infection due to occupational exposure. It is important to diagnose TB infections in HCWs to prevent nosocomial transmission, particularly among immunocompromised patients.ObjectiveThe aim of this study was to analyze the rate of tuberculin skin test (TST) conversion and to assess the incidence of active TB after the latent TB infection screenings in high-risk HCWs.MethodsThis retrospective cohort study involved 458 HCWs in TB-related departments between 2009 and 2013. All HCWs underwent a TST and a chest radiograph annually; an interferon-γ release assay (IGRA) was performed on the TST-converted subjects. TST-converted and IGRA-positive HCWs underwent treatment for latent TB infection.ResultsThe TST conversion rate was 30.3% from 2009 to 2011 in two years, 7.4% from 2011 to 2012, and 17.4% from 2012 to 2013. Eleven subjects out of 42 TST converters (26%) were IGRA-positive; two of them developed into active pulmonary TB during the follow-up period.ConclusionsThere was significant discordance between TST conversion and IGRA results in high-risk HCWs, and active TB developed only in TST-converted and IGRA-positive HCWs. Therefore, the combined use of TST and IGRA for periodic monitoring of TB infections in high-risk HCWs may be useful.

P531 Tuberculin skin test conversion rate in inflammatory bowel disease patients receiving anti-TNFα agents

Anti-TNFα therapy increases the risk of tuberculosis (TB) (re)-activation in inflammatory bowel disease (IBD) patients. Purified protein derivative tuberculin skin test (PPD-TST) is considered a pre-requisite at baseline. However, few data exist regarding the kinetics of this test during therapy. Therefore, our study investigated the conversion rate of PPD-TST in IBD patients under anti-TNFα treatment. Anti-TNFα treated IBD patients followed up in our centre with a baseline PPD-TST underwent a sequential one during therapy. Those with a positive PPD-TST either at baseline or during therapy (d > 10 mm in naïve and d > 5 mm in those exposed to immunomodulators [IMS]) received 300 mg isoniazid orally for 9 months. Sixty-eight IBD patients have been enrolled so far (males: 51.47%, Crohn’s disease: 82.35%). Median age at IBD diagnosis was 33.1 years [IQR: 20.3, range: 16.7–66.7]. Median duration of IBD was 7.7 months [IQR: 9.8, range: 1.4–32.7]. Nine patients (13.23%) had a positive PPD-TST at baseline. Fifty-eight patients have undergone a second PPD-TST (median time between the first and second PPD-TST: 27.10 months [IQR: 41.22, range: 6.3–190.1]). Nineteen patients were under combination therapy with an IMS at the second PPD-TST. In seven patients with a positive baseline PPD-TST, this remained positive (in five patients the diameter was decreased and in two increased) and in one it turned negative. Out of the remaining 50 patients with a negative baseline PPD-TST, 10 (20%) exhibited a positive second PPD TST; three of them were receiving infliximab for less than 3 years and seven of them adalimumab (three for less and four for more than 3 years). Only 3 of 10 were under combination therapy. No case of active tuberculosis has been detected in this cohort so far. All patients with a PPD-TST conversion received anti-tuberculous treatment. A positive PPD-TST followed by anti-TB treatment before the initiation of anti-TNFα in IBD patients was not associated with an increased rate of TB infection during therapy. In one-fifth of the patients with a negative baseline PPD-TST the test exhibited conversion but without any undesirable consequence if so treated.

LATENT TUBERCULOSIS AMONG PROFESSIONALS FROM A REFERRAL HOSPITAL IN ONCOLOGY

Introduction: Tuberculosis (TB) is an ancient contagious disease, and continues to be the leading cause of morbidity and mortality among infectious contagious diseases. It can be considered an occupational infectious disease when it happens in health professionals. These professionals are directly exposed to TB and are considered to be a high risk population for latent tuberculosis infection (LTBI) and active TB. The primary aim of this study was to estimate the prevalence of LTBI among the clinical and administrative staff of an oncology referral hospital in Rio Grande do Sul. The secondary aim of this study was evaluate tuberculin skin test (TST) conversion rate and the risk factors for TST positivity in this population. Methods : A cross-sectional study was carried out in a retrospective cohort with data collected in March 2013 and March 2014. Data of professionals from different hospital units were included. Those with induration ≥ 10 mm were considered as reactors, and conversion rate was assessed by an increase ≥ 10 mm in induration in the second TST compared with the first one. Results: Among the 225 professionals evaluated in 2013, 135 (60%) were reactors and 90 (40%) were non-reactors. The mean age was 32.9 (± 9.55), 176 (78.22%) were female, and most of the reactors worked in the hospital for 4 years or less. Non-reactors in 2013 were recommended to repeat the test in 2014, and the conversion rate was 9.37%. There was no significant difference in prevalence among the different professional categories, and the assessed risk factors were not associated with ILTB. Conclusions: The prevalence of LTBI in the study population was high, reinforcing the need to implement effective control measures to prevent LTBI in the hospital where the study was conducted. Keywords: Latent tuberculosis; occupational risk; tuberculin test; vulnerable populations

Institutional Tuberculosis Transmission. Controlled Trial of Upper Room Ultraviolet Air Disinfection: A Basis for New Dosing Guidelines.

Transmission is driving the global tuberculosis epidemic, especially in congregate settings. Worldwide, natural ventilation is the most common means of air disinfection, but it is inherently unreliable and of limited use in cold climates. Upper room germicidal ultraviolet (UV) air disinfection with air mixing has been shown to be highly effective, but improved evidence-based dosing guidelines are needed. To test the efficacy of upper room germicidal air disinfection with air mixing to reduce tuberculosis transmission under real hospital conditions, and to define the application parameters responsible as a basis for proposed new dosing guidelines. Over an exposure period of 7 months, 90 guinea pigs breathed only untreated exhaust ward air, and another 90 guinea pigs breathed only air from the same six-bed tuberculosis ward on alternate days when upper room germicidal air disinfection was turned on throughout the ward. The tuberculin skin test conversion rates (>6 mm) of the two chambers were compared. The hazard ratio for guinea pigs in the control chamber converting their skin test to positive was 4.9 (95% confidence interval, 2.8-8.6), with an efficacy of approximately 80%. Upper room germicidal UV air disinfection with air mixing was highly effective in reducing tuberculosis transmission under hospital conditions. These data support using either a total fixture output (rather than electrical or UV lamp wattage) of 15-20 mW/m(3) total room volume, or an average whole-room UV irradiance (fluence rate) of 5-7 μW/cm(2), calculated by a lighting computer-assisted design program modified for UV use.

Tuberculin skin test conversion rate among short-term health care workers returning from Gaborone, Botswana

Our objective was to determine tuberculin skin test conversion rate of health care workers traveling to Botswana. The rate of tuberculin skin test conversion was 4.2% for the entire group studied or 6.87 per 1000 person weeks (95% CI, 1.87-17.60). International travel by health care workers traveling from low incidence countries to areas of the world where tuberculosis is highly endemic places the health care worker at an increased risk of acquiring tuberculosis. To determine the tuberculin skin test conversion rate of health care workers living in the United States with previously negative tuberculin skin test results working for less than 1 year in a hospital in Botswana where tuberculosis is highly endemic. We performed a cross-sectional survey among health care workers affiliated with the University of Pennsylvania School of Medicine who participated in patient care in Botswana between July 1st 2004 and June 30th 2009. We recruited health care workers after returning from Botswana who had a documented negative tuberculin skin test in the year prior to travel, who spent at least 2 weeks but not more than 1 year and who had a documented tuberculin skin test 2-3 months post travel. The main study outcome was a positive tuberculin skin test 6-12 weeks after returning from Botswana, defined by an area of at least 10mm induration 48-72h after placement of the tuberculin skin test. 95 Subjects participated in the study and there were 4 tuberculin skin test conversions. The rate of tuberculin skin test conversion in our study population was 4.2% for the entire group studied or 6.87 per 1000 person weeks (95% CI, 1.87-17.60). The tuberculin skin test conversion rate was higher than the reported conversion rates for those not working in a health care setting.

AB0363 Rate of tuberculin skin test or interferon gamma release assay conversion during anti-tumor necrosis factor therapy in rheumatic patients

BackgroundDespite negative baseline testing for tuberculosis (TB) with traditional (tuberculin skin test/TST, chest X-ray/CXR) or newer (interferon-gamma release assays/IGRAs) screening methods, a small number of patients receiving anti-tumor necrosis factor...

How frequently do tuberculosis screening tests convert in inflammatory bowel disease patients on anti-tumour necrosis factor-alpha? A pilot study

Tuberculosis reactivation can lead to severe complications in patients treated with anti-tumour necrosis factor-alpha. To assess the usefulness of repeat tuberculosis screening tests in inflammatory bowel disease patients on stable anti-TNF therapy. Cross-sectional study, in patients on prolonged anti-TNF treatment (≥ 12 months) and basal negative screening for latent tuberculosis. Quantiferon(®)-TB Gold In-tube test was performed and then, tuberculin skin test was administered. 74 patients were included, median duration of anti-TNF treatment was 30 months (IQR 19-54); 47 patients on infliximab and 27 on adalimumab; no patient was on glucocorticoids. Previous BCG vaccination was present in 5 cases. After anti-TNF was started, 4 patients suffered from potential tuberculosis exposure and two cases travelled to endemic areas. The cumulative incidence of tuberculin skin test conversion was 2.7% (95% CI 0.3-9.4%, 2/74), and the incidence rate of tuberculin skin test conversion was 0.83% (95% CI 0.1-2.9%) per patient-year of treatment with anti-TNF drugs. All Quantiferon tests but one (a patient with an indeterminate result and a negative tuberculin skin test) were negative. The incidence rate of conversion of tuberculosis screening tests among patients on anti-TNF treatment seems to be low and these conversions were diagnosed based on a positive tuberculin skin test and were discordant with Quantiferon testing.

Occupational Infections among Health Care Workers in a Secondary Care Hospital Saudi Arabia

Introduction: Healthcare workers (HCWs) are frequently exposed to various infectious agents while performing their duties and many accidental exposures to blood borne and air borne pathogens are preventable if health care workers comply with appropriate precautions. Objectives: Assessment of some occupational exposure among health care workers in a secondary care hospital- Najran province- Saudi Arabia during the period (2009-2012). Subjects and methods: Retrospective review of health care workers’ (HCWs) records from staff health clinic to determine the distribution of occupational infections among different job categories which was confirmed by clinical manifestations, laboratory investigations and reports of needle stick incidents to which HCWs were exposed during period of data collection. Results: The most common occupational infection among healthcare workers was chicken pox. There was low Tuberculin skin test (TST) conversion rate among different professional categories and nurses were the most affected occupational category during the study period as regard exposure to sharp injuries and air borne infections. Conclusions: Management policy and procedures should be directed and implemented to minimize and prevent occupational infections with emphasis on nurses as being the highly affected risk group.

Comparative evaluation of phenol and thimerosal as preservatives for a candidate vaccine against American cutaneous leishmaniasis

For decades thimerosal has been used as a preservative in the candidate vaccine for cutaneous leishmaniasis, which was developed by Mayrink et al. The use of thimerosal in humans has been banned due to its mercury content. This study addresses the standardization of phenol as a new candidate vaccine preservative. We have found that the proteolytic activity was abolished when the test was conducted using the candidate vaccine added to merthiolate (MtVac) as well as to phenol (PhVac). The Montenegro's skin test conversion rates induced by MtVac and by PhVac was 68.06% and 85.9%, respectively, and these values were statistically significant (p < 0.05). The proliferative response of peripheral mononuclear blood cells shows that the stimulation index of mice immunized with both candidate vaccines was higher than the one in control animals (p < 0.05). The ability of the candidate vaccines to induce protection in C57BL/10 mice against a challenge with infective Leishmania amazonensis promastigotes was tested and the mice immunized with PhVac developed smaller lesions than the mice immunized with MtVac. Electrophoresis of phenol-preserved antigen revealed a number of proteins, which were better preserved in PhVac. These results do in fact encourage the use of phenol for preserving the immunogenic and biochemical properties of the candidate vaccine for cutaneous leishmaniasis.

Protecting health care workers from tuberculosis: A 10-year experience

Cook County Hospital (CCH) is an inner-city, large public hospital. Twenty-five percent of Chicago's tuberculosis (TB) cases are diagnosed at CCH. We wanted to review and analyze interventions implemented over a 10-year period at CCH to prevent TB infection in health care workers. We performed a retrospective review of interventions to prevent health care-associated tuberculosis. We collated and analyzed tuberculin skin test conversions in our employees for the same time period. From 1990 to 2002, we cared for over 1800 in-patients with tuberculosis. During 1992-1997, multiple interventions to eliminate health care-associated spread of tuberculosis were implemented. Tuberculin skin test conversions in our employees decreased markedly from January 1994 through December 2002. Two drops in tuberculin skin test conversion rates occurred: one after introduction of basic administrative and engineering controls and a second after we experienced a decrease in missed TB cases and the introduction of N-95 personal respirators with 1-time qualitative fit testing. Our annual health care worker skin test conversion rate fell significantly when our primary interventions were relatively simple administrative and engineering controls. Educating health care workers to promptly recognize patients with TB and placing exhaust fans to create negative-pressure respiratory isolation rooms were probably our 2 most potent infection control measures.

Differences in Tuberculin Reactivity as Determined in a Veterans Administration Employee Health Screening Program

In response to a difference in pricing, the San Diego Veterans Administration Medical Center changed its tuberculin preparation from Tubersol to Aplisol in the fall of 2006. Following the change, an increased number of employee skin test conversions was noted. Employee tuberculin skin test converters from 2006 were screened with the QuantiFERON Gold (QFT-G) gamma interferon release assay. Those employees who tested negative by QFT-G were asked to repeat their skin test with both Tubersol and Aplisol tuberculin preparations. Of the new purified protein derivative converters, 12 of 14 returned for repeat testing with QFT-G, and the assay was negative for 83% (10/12), positive for 8% (1/12), and indeterminate for 8% (1/12) of the individuals. Nine of the individuals who were QFT-G negative agreed to repeat skin testing with both tuberculin preparations, and 7/8 (87.5%) demonstrated reactivity with the Aplisol preparation, while 0/8 (0%) reacted to the Tubersol preparation. A change from Tubersol to Aplisol resulted in elevated tuberculin skin test conversion rates that may be due to false-positive reactions. The differences in skin test reactivity between preparations support CDC guidelines that recommend that institutions should not change tuberculin preparations, as doing so may falsely increase the number of positive reactions.

Acute Respiratory Infections in a Recently Arrived Traveler to Your Part of the World*

Many acute infectious pulmonary diseases have incubation periods that are long enough for travelers to have symptoms after returning home to a health-care system that is not familiar with “foreign” infections. Respiratory infections have a relatively limited repertoire of clinical manifestations, so that there is often nothing characteristic enough about a specific infection to make the diagnosis obvious. Thus, the pathway to the diagnosis of infections that are not endemic in a region relies heavily on taking a thorough history of both itinerary and of specific exposures. One important caveat is that on occasion, the history of a recent trip creates an element of “tunnel vision” in the evaluating health-care provider. It is tempting to relate a person's problem to that recent trip; however, when evaluating recent returnees, it is always important to remember that the travel may have nothing to do with the patient's presentation. Recent travel may add diagnostic considerations to the list of possibilities, but an astute clinician must not disregard the possibility that the patient's illness has nothing to do with the recent trip.

A university hospital's 10-year experience with tuberculin testing: Value of the 2-step tuberculin skin test

The usefulness of the 2-step tuberculin skin test as a tool for monitoring tuberculosis exposure among health care workers is controversial. We aimed to determine the cost-effectiveness and influence of initiation of a preemployment, 2-step tuberculin skin-testing program on the annual tuberculin skin conversion rate among a university hospital's health care workers. The tuberculin skin test conversion rates among the recipients of 31,729 tuberculin skin tests over 10 years were retrospectively analyzed. Data from the first 6 years of this study were generated when a single preemployment tuberculin skin test was utilized. Data from the last 4 years were gathered after the advent of a preemployment 2-step program. A cost analysis of the 2-step tuberculin skin test process was performed to determine the annual cost of this program. Relative risk of a conversion was 8.43 times less during the 2-step period when compared with the years when a single tuberculin skin test was given at the start of employment (P < .001). A cost analysis showed that the annual added cost of the 2-step program was approximately 9,565 US dollars. A greater than 8-fold reduction in the number of annual tuberculin skin test conversion coincided with, but could not be attributed solely to, the initiation of a 2-step program in our hospital. The Infection Control Committee concluded that the 2-step testing program is essential to achieve the hospital's goal of a 0% annual tuberculin skin test conversion rate and that the annual cost is justified.

Tuberculin skin test conversion and reactivity rates among adults with and without human immunodeficiency virus in urban settings in Ethiopia.

To investigate whether low CD4+ T-cell counts in healthy and human immunodeficiency virus (HIV)-infected Ethiopians influence tuberculosis (TB) immunological memory, tuberculin skin test (TST) conversion and reactivity rates were investigated among adults with and without HIV infection in urban settings in Ethiopia. Reaction to the TST was analyzed with purified protein derivative by the Mantoux technique. A total of 1,286 individuals with TST results of > or = 5-mm (n = 851) and < or = 4-mm (n = 435) induration diameters were included. Individuals with < or = 4-mm induration sizes were followed up for 21.4 +/- 9.5 months (mean +/- standard deviation) to observe skin test conversion. The overall TST reactivity (> or = 5-mm induration diameter) was 66.2% (n = 851). Reactivity was significantly lower among HIV-positive persons (40.5%) than among HIV-negative persons (68.7%) (P < 0.001). Of the above persons, 32 incident TB patients were checked for their TST status 13.05 +/- 11.1 months before diagnosis and reactivity was found among 22 (68.7%) of them. Of the TST-negative persons with 0- to 4-mm indurations who were followed up for 3 years, the conversion rate to positivity was 17.9/100 person-years of observation (PYO) (14.4/100 PYO and 18.3/100 PYO in HIV-positive and -negative persons, respectively). Despite lower absolute CD4+ T-cell numbers in Ethiopians, higher TST conversion and reactivity rates show the presence of a higher rate of latent TB infection and/or transmission. The lower TST positivity rate before a diagnosis of TB disease showed the lower sensitivity of the test. This indicates the need for other sensitive and specific diagnostic and screening methods to detect TB infection, particularly among HIV-positive persons, so that they can be given prophylactic isoniazid therapy.

StaffTRAK-TB: software for surveillance of tuberculosis infection in healthcare workers.

The Centers for Disease Control and Prevention (CDC) recommends periodic tuberculin skin testing of healthcare workers with potential exposure to Mycobacterium tuberculosis. However, many healthcare facilities have neither a system to identify workers due for their skin test nor a means of analyzing aggregate data. To illustrate some of the complexities involved in tuberculin skin test (TST) tracking and analysis, and how these might be addressed, this report describes a software package called staffTRAK-TB, developed by the CDC to facilitate surveillance of tuberculosis infection in healthcare workers. staffTRAK-TB records data for each healthcare worker, including demographic information, occupation, work location, multiple TST results, and results of evaluations to determine if clinically active tuberculosis is present. Programmed reports include lists of workers due and overdue for skin tests, and skin test conversion rates by occupation or worksite. Standardization of types of occupations and locations allows data from multiple facilities to be aggregated and compared. Data transfer to the CDC can be performed via floppy diskettes. staffTRAK-TB illustrates important issues in software structure, standardization of occupation and work-location information, relevant data items, and reports and analyses that would be useful in practice. Developing software that adequately addresses the epidemiological issues is complex, and the lessons learned may serve as a model for hospital epidemiologists, infection control personnel, occupational health personnel, and computer programmers considering software development in this area or trying to optimize their facility's TST surveillance.

Tuberculin skin test conversion rate in dental health care workers—results of a prospective study

Objectives: The tuberculin skin test conversion rate over 12 months in dentists, dental hygienists, and dental assistants was assessed in 3 US-Mexico border counties of Texas in which reported tuberculosis rates were high compared with the rates for Texas and the United States. Methods: Tuberculin skin tests were administered to 284 subjects and repeated on nonreactors 12 months later. Participants also completed self-administered questionnaires. Results: The baseline positive tuberculin skin test prevalence was 4.6%. Nonreactors were more likely to have been born in the United States ( P < .001). The tuberculin skin test conversion rate over 12 months was 1.7%. Conclusion: Results indicate a need for heightened awareness of tuberculosis transmission and annual surveillance by dental health care workers, as recommended by the Centers for Disease Control and Prevention. (AJIC Am J Infect Control 1999;27:385-7)

Tuberculin Test Conversion among Employees of a Tertiary Care Hospital in Riyadh, Saudi Arabia

The objective of this study was to determine the tuberculin skin test conversion rate, as well as the course and outcome of the converters, among employees of a tertiary care hospital. The study is a retrospective, cohort descriptive study undertaken at the King Faisal Specialist Hospital and Research Centre, in Riyadh, Saudi Arabia. The study was undertaken over a four-year period from 1993 to 1996, and the subjects were employees who had annual screening PPD skin tests. The outcome measures skin test conversion, prophylactic treatment with isoniazid (INH), side effects, and development of clinical tuberculosis. A total of 6883 tuberculin skin tests were performed during the study period. The mean annual conversion rate was 1.55%. About 78% of the converters received INH prophylaxis, but only 75% of those who started chemoprophylaxis completed the course. The side effects of INH treatment were found in 23% of those on treatment, and one of the converters developed clinically active tuberculosis during the study period. At the King Faisal Specialist Hospital and Research Centre, the mean annual tuberculin skin test conversion rate among employees is similar to that found in other studies, but compliance to oral isoniazide prophylaxis is low. There is a need to develop strategies to improve compliance.

Tuberculin Skin Test Conversion Rates in New York City Emergency Medical Service Health Care Workers

Objective: To determine annual tuberculin skin test conversion (infection) rates for prehospital health care workers (EMTs and paramedics) in an urban environment with a high prevalence of Mycobacterium tuberculosis Methods: We conducted a prospective study of prehospital health care workers for the New York City EMS, EMS Employee Health Service, and the Fire Department Bureau of Health Service to determine the tuberculin skin test conversion rates. In 1992, all current and new EMS prehospital health care workers without a known history of a positive tuberculin reaction received a baseline tuberculin purified protein derivative (PPD) skin test. Thereafter, (January 1, 1993–December 31, 1996) all EMS health care workers who had negative PPD skin test results received annual tuberculin PPD skin tests. Tuberculin skin test conversion was defined as induration of 10 mm or greater in a worker with a documented prior negative test result. The PPD skin test reaction was measured by trained professional readers. Results: A total of 7,290 PPD test results were read during this study. Compliance with annual testing was 75%. Annual tuberculin skin test conversion rates were 1.3% in 1993, .7% in 1994, .1% in 1995, and .2% in 1996 (average .5%). In a static subgroup with at least 15 years’ seniority, compliance with annual testing was 100% and annual tuberculin skin test conversion rates were .5% in 1993, 0 in 1994, .5% in 1995, and 1.5% in 1996 (average .6%). Conclusion: Despite the high prevalence of M tuberculosis infection in New York City and the potential for difficulty in the use of respiratory precautions during emergency response operations, EMS prehospital health care workers have an annual tuberculin conversion rate that is relatively low compared with hospital-based health care workers. [Prezant DJ, Kelly KJ, Mineo FP, Janus D, Karwa ML, Futterman N, Nolte C: Tuberculin skin test conversion rates in New York City emergency medical service health care workers. Ann Emerg Med August 1998;32:208-213.]