Surveillance of health-care workers (HCWs) for tuberculosis (TB) and assessment of TB transmission through routine periodic screening with tuberculin skin tests (TSTs) are essential components of effective TB-control programs in health-care settings (1). Based on TST results, risk for acquiring new infections can be assessed and infection-control practices modified accordingly. In 1993, a self-administered mail survey was conducted to characterize the TST practices and results among dentists in the Indian Health Service (IHS) and the Federal Bureau of Prisons (FBoP). This report summarizes the findings of the survey.

In July 1993, a pretested questionnaire and a letter describing the purpose of the study were mailed to all dentists employed by IHS (n=389) and FBoP (n=120). IHS dentists provide clinical services in 200 dental clinics in IHS/tribal hospitals or ambulatory health centers in 33 states. Within the FBoP, inmates receive dental treatment at 107 dental clinics.

Of the 509 dentists who were mailed the questionnaire, 489 (96% {372 IHS and 117 FBoP}) responded. Of the 489, 194 (40%) dentists had practiced clinical dentistry in the IHS or FBoP for less than 3 years; 183 (37%), 3-9 years; and 112 (23%), greater than or equal to 10 years. The mean years of clinical practice were similar for dentists in both groups (5.9 years for IHS and 5.6 years for FBoP dentists; p=0.7, two-tailed t-test); 438 (90%) reported that they were practicing clinical dentistry at the time of the survey (87% IHS and 97% FBoP), and the remainder were in nonclinical positions.

Almost all (474 {97%}) respondents reported ever having received a TST (365 {98%} IHS and 109 {93%} FBoP); 92% of those tested reported always having a negative test result (Table_1). Of 36 dentists who reported ever having a reactive TST, 17 (47%) reported the first reactive TST occurred after graduation from dental school. Of these 17 dentists, 14 (11 IHS and three FBoP) reported converting from a negative TST to a reactive TST.

Among respondents who reported ever being tested, the most frequent reason for testing was "as part of a TST program among health care personnel" (82%). In addition, 8% received a TST at the beginning of employment or during a routine physical examination; 6% received a TST as both part of a TST program and as a result of exposure; 1%, as the result of an exposure to TB; and 3%, for other reasons.

Almost half (46%) of respondents who were currently in clinical practice reported having ever been exposed to someone with active TB; of these dentists, 93% identified a dental patient as one of several possible sources of exposure; 6%, a co-worker; 3%, a personal acquaintance/friend; and 3%, a family member. The percentage of currently practicing dentists who reported ever having been exposed to a dental patient with active TB increased with years of clinical practice (p less than 0.01, chi-square test for linear trend). As a result of an exposure to a dental patient with active TB, 42% reported receiving a postexposure TST.

Among 425 respondents who were currently in clinical practice and reported having ever been tested, 80% received a TST within the 3 years preceding the survey. Of these 80%, 75% reported having a TST at routine intervals: annually (68%), semiannually (4%), and biannually (3%). The remaining 25% indicated they received TSTs at routine physical examinations, at the beginning of employment, or as the result of exposure to a person with active TB. The percentage of currently practicing dentists reportedly skin tested during the 3 years preceding the survey decreased with increasing years of clinical practice in the IHS or FBoP (p less than 0.01, chi-square test for linear trend); 90% practicing less than 3 years had been tested during the preceding 3 years, compared with 68% who had practiced greater than or equal to 10 years.

Reported by: Dental Svcs Br, Indian Health Svc. Health Svcs Div, Federal Bur of Prisons. Office of the Chief Dental Officer, Public Health Svc. Div of Tuberculosis Elimination; Surveillance, Investigations, and Research Br, Div of Oral Health, National Center for Prevention Svcs, CDC.

Editorial Note

Editorial Note: The findings of this survey suggest that nearly all dentists employed by IHS and FBoP had received a TST. Although 80% of those currently practicing had been tested during the 3 years preceding the survey, less than 60% had been tested at least annually, in accordance with current recommendations (1). Even though these recommendations advise that HCWs be evaluated following exposure to TB, less than half of the dentists in this survey who reported exposure to a patient with active TB received a postexposure TST.

Previous reports in other health-care settings suggest that transmission is most likely to occur from patients with unrecognized active TB (2-5). The dentists in this report may be at occupational risk for TB infection: almost half of currently practicing dentists reported previous exposure to a dental patient with active TB, and the dentists treat patients known to be at increased risk for TB (1). Despite this increased risk, the prevalence of reactive TSTs among the dentists in this survey is consistent with the estimated prevalence of TB in the general U.S. population (6) but lower than that reported among some groups of nondental HCWs (7,8). Neither the type or date of the TST nor the size of the TST reaction for those dentists who reported having a reactive TST could be verified.

Summary data of TSTs of dental workers and other HCWs should be periodically reviewed to evaluate the potential risk for transmission of TB among HCWs. Dental workers and other HCWs should be tested at the beginning of employment and at least annually thereafter (1). However, because the risk for exposure to TB may vary in relation to different factors (e.g., the prevalence of TB in the patient population), the frequency of retesting should be established according to the risk for acquiring new infection in a specific facility, particularly in settings where risk for TB transmission may be greater. The findings in this report are being used to assist efforts to increase awareness of and compliance with recommendations for TSTs within IHS and FBoP clinical dental programs.

References

1. CDC. Guidelines for preventing the transmission of tuberculosis in health-care settings, with special focus on HIV-related issues. MMWR 1990;39(no. RR-17).

2. Edlin BR, Tokars JI, Grieco MH, et al. An outbreak of multidrug-resistant tuberculosis among hospitalized patients with the acquired immunodeficiency syndrome. N Engl J Med 1992; 326:1514-21.

3. Pearson ML, Jereb JA, Frieden TR, et al. Nosocomial transmission of multidrug-resistant Mycobacterium tuberculosis: a risk to patients and health care workers. Ann Intern Med 1992;117:191-6.

4. Beck-Sague C, Dooley SW, Hutton MD, et al. Hospital outbreak of multidrug-resistant Mycobacterium tuberculosis infections: factors in transmission to staff and HIV-infected patients. JAMA 1992;268:1280-6.

5. Dooley SW, Villarino ME, Lawrence M, et al. Nosocomial transmission of tuberculosis in a hospital unit for HIV-infected patients. JAMA 1992;267:2632-4.

6. Bloom BR, Murray CJL. Tuberculosis: commentary on a reemergent killer. Science 1992; 257:1055-64.

7. Barrett-Connor E. The epidemiology of tuberculosis in physicians. JAMA 1979;241:33-8.

8. Price LE, Rutala WA, Samsa GP. Tuberculosis in hospital personnel. Infect Control 1987;8:97-101.

Table_1
Note: To print large tables and graphs users may have to change their printer settings to landscape and use a small font size.

TABLE 1. Percentage of Indian Health Service and Federal Bureau of Prisons
dentists reporting tuberculin skin test (TST) results, 1993
================================================================================
                       Indian Health Service     Federal Bureau of Prisons
                              (n=365)                     (n=109)
                       ---------------------     -------------------------
TST results                No.        (%)          No.             (%)
--------------------------------------------------------------------------
Always negative            337        (92)         101             (93)
Reactive before dental
  school graduation *       14        ( 4)           5             ( 5)
Reactive after dental
  school graduation *       14        ( 4)           3             ( 3)
--------------------------------------------------------------------------
* Includes dentists who reported always having a reactive TST and dentists who
  reported changing from negative to reactive.
================================================================================

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