Two-step Skin Test Research Articles

A data driven policy to minimise the tuberculosis testing cost among healthcare workers.

IntroductionThe Centres for Disease Control and Prevention (CDC) mandates that healthcare employees at high‐risk exposure to Tuberculosis (TB) undergo annual testing. Currently, two methods of TB testing are used: a two‐step skin test (TST) or a whole‐blood test (IGRA). Healthcare leadership's test selection must account for not only direct costs such as procedure and resources but also indirect costs, including employee workplace absence.MethodsA mathematical model based on Upstate South Carolina's largest health system affecting over 18,000 employees on six campuses was developed to investigate the value loss perspective of these testing methods and assist in decision‐making. A process flow map identified the varied direct and indirect costs for each test for four employee types, and 6 travel‐to‐testing‐site times were calculated.ResultsThe switching point between testing procedures that minimised total system costs was most influenced by employee salary compared to travel distance. Switching from the current hospital policy to an integrated TST/IGRA testing could reduce TB compliance costs by 28%.ConclusionsThis study recommends an integrated approach as cost‐effective for large health systems with multiple campuses while considering the direct and indirect costs. When accounting for ‘inconvenience costs’ (stress, etc.) associated with visits, IGRAs are recommended irrespective of employee salary.

Risk Factors for Tuberculosis Conversion in a State Prison

A case-control study determined the risk factors for latent tuberculosis (TB) conversion among Oregon Department of Correction (ODOC) inmates from July 2000 - July 2001. The first objective was to identity the converters. These were inmates who tested negative for the Purified Protein Derivative (PPD) skin test on entry and subsequently tested positive on annual testing. The second objective was determining the risk factors for conversion by comparing the converters with randomly selected controls. The Correctional Information System (CIS) and Mental Health databases were accessed to obtain health and demographic information. With ninety-nine percent of PPD positive inmates on anti-tuberculosis medications, nearly all male inmates who tested positive from July 00-01 (n = 307) were identified through the ODOC pharmacy records. A medical chart review (276 of 307 or 90%) separated the converters (n = 72) from the reactors who tested positive on entry (n = 123) and the prior positives on medications (n = 81). The conversion rate was 5.0 per 1,000 person-years. Differences between the cases (converters) and controls were analyzed using multivariate logistic regression. The converters were 6 times more likely to be Latino (p < .005) vs. Caucasian, over 19 times less likely to live in medium vs. minimum (p < .001) or maximum vs. minimum (p < .001) security prisons, and over 5 times less likely to live in a medium vs. low (.012 < p < .031) or high vs. low (.002 < p < .007) density prison. They had 1.4-1.5 times fewer PPD skin tests (.002 < p < .009) and lived in 1.5-1.7 times fewer prisons (.005 < p < .017). Age, education, county of incarceration, number of incarcerations, and number of visitors were not found to be significant variables. The results revealed a low conversion rate compared to other U.S. prisons. Prison health officials should consider performing two-step skin testing in order to distinguish the booster phenomenon from intramural conversion.

Standardization and Prevalence of the Booster Phenomenon: Evaluation Using a Two-Step Skin Test with 43kDa Glycoprotein in Individuals from an Endemic Region of Paracoccidioidomycosis.

We estimated the occurrence rate of the booster phenomenon by using an intradermal test with 43kDa glycoprotein in an endemic area of paracoccidioidomycosis in the central-west region of Brazil. Individuals who had a negative result on a survey performed by using an intradermal test with 43kDa glycoprotein in an endemic area of paracoccidioidomycosis underwent a second intradermal test after 10-15days to determine the presence or absence of the booster phenomenon. Statistical analyses were performed using the Chi-square test, Chi-square for linear trend test, Student's t test, and binomial test; p<0.05 was considered significant. For the first time, we reported the occurrence of the booster phenomenon to an intradermal reaction caused by 43kDa glycoprotein at a rate of 5.8-8.4%, depending on the test's cutoff point. This suggests that a cutoff point should be considered for the booster phenomenon in intradermal tests with 43kDa glycoprotein: a difference of 6-7mm between readings according to the first and second tests, depending on the purpose of the evaluation. The results indicate that the prevalence of paracoccidioidal infection in endemic areas is underestimated, as the booster phenomenon has not been considered in epidemiological surveys for this infection.

Routine two-step skin testing for tuberculosis in the staff of a geriatric hospital in Israel: booster and conversion rates

The objective of this study was to determine the prevalence of positive skin tests amongst the staff of a 200 bed geriatric hospital in Haifa, Israel. By comparing the findings with those of a study performed five years previously, we hoped to ascertain the number of conversions which had occurred in the period studied. This was undertaken in order to assess a new policy from the Israel Ministry of Health regarding skin testing for health care workers. We also hoped to decide upon the frequency of skin testing required and to compare data from recent immigrants from countries with a high prevalence of TB. In 1997, we performed two-step skin testing (TSST) on 318 health care workers. We ascertained the number of positive reactions on the first and second testing and calculated the number of subjects who showed significant boosting. We also compared the results to those obtained in a study in 1992 and calculated the rate of conversion. We used multivariate analysis to examine the effects of age, gender, country of origin, years in Israel, previous BCG vaccination, previous exposure to contagious TB, work site and area of residence in the city, on the response to TSST. Between 1990 and 1996, 655 000 immigrants from the former USSR arrived; ‘recent immigration’ was defined from that date onward. The final number of positive reactions out of 282 subjects, who were either positive or negative on step 1 and presented for step 2, was 171 (60%).Booster effect was not significantly associated with any of the variables examined. The size of reaction in TSST was related to country of origin and recent immigration. The 83 recent immigrants from the former USSR had more frequent (61%) and larger reactions (mean (sd): 9.0 (6.46) mm) than the 114 native-born Israelis with 39% positive reactions (6.2 (5.89) P= 0.009). Comparison with 1992 revealed 26 (31%) of previous negatives as positive. Conversion was associated with age. All conversions save one were in individuals younger than 50 years (P= 0.07). In conclusion, TSST, performed to enable detection of recent infection after exposure to contagious TB, was relevant for 40% of health care workers (HCWs). Second step testing contributed an additional 23% positive reactions. New immigrants had larger initial reactions. Conversion occurred mostly in younger workers and could be either due to unrecognized TB in the hospital or to exposure in the community.

Cost-effectiveness of the two-step skin test for tuberculosis screening of employees in a community hospital.

To assess the frequency of the booster effect as well as the need for and the cost effectiveness of the two-step skin test for tuberculosis screening at our medical center, we conducted a pilot study from June 1980 to March 1983 with hospital and clinic employees. Six (0.4%) of 1,521 employees tested by the two-step skin test demonstrated the booster effect. The mean age of these six employees was 35 years (range, 24 to 44 yr). During the study period, 10 employees converted to a positive skin test. The booster effect would have accounted for approximately 38% (6 of 16) of those converting if the two-step testing were not performed. At our medical center, the additional cost of the two-step skin test was low and justifiable for medical and epidemiologic reasons. We suggest that each hospital review the prevalence of tuberculosis among its patient and employee populations. The need for and cost effectiveness of the two-step skin test for new hospital employees must be re-examined on the basis of these data.