Interobserver and method variability in tuberculin skin testing

A simple protocol for tuberculin skin test reading certification

Although tuberculosis preventive therapy is one of the cornerstones for eliminating the disease, many barriers exist in the cascade of care for latent tuberculosis infection, including the need to certify healthcare professionals for reading tuberculin skin tests (TST). This paper proposes and evaluates a simple protocol for TST reading training. Primary care workers from different backgrounds received a 2-hour theoretical course, followed by a practical course on bleb reading. Blebs were obtained by injecting saline into sausages and then in volunteers. A certified trainer then evaluated the effectiveness of this protocol by analyzing the trainees' ability to read TST induration in clinical routine, blinded to each other's readings. Interobserver agreement was analyzed using the Bland-Altman test. The trainees' reading accuracy was calculated using two cut-off points - 5 and 10mm - and the effect of the number of readings was analyzed using a linear mixed model. Eleven healthcare workers read 53 saline blebs and 88 TST indurations, with high agreement for TST reading (0.07mm average bias). Sensitivity was 100% (94.6; 100.0) at 5mm cut-off and 87.3% (75.5; 94.7) at 10mm cut-off. The regression model found no effect of the number of readings [coefficient: -0.007 (-0.055; 0.040)]. A simple training protocol for reading TST with saline blebs simulations in sausages and volunteers was sufficient to achieve accurate TST induration readings, with no effect observed for the number of readings. Training with saline blebs injected into voluntary individuals is safer and easier than the traditional method.

Utility of Dual Skin Tests to Evaluate Tuberculin Skin Test Reactions of 10 to 14 mm in Healthcare Workers

Objective:

To define the utility of 10- to 14-mm reactions to a Mycobacterium tuberculosis purified protein derivative (PPD) skin test for healthcare workers (HCWs).

Design:

Blinded dual skin testing, using PPD and M. avium sensitin, of HCWs at a single medical center who had a 10-to 14-mm reaction to PPD when tested by personnel from the Occupational Health Department as part of routine annual screening.

Setting:

A single tertiary-care academic medical center.

Participants:

Employees of the medical center who underwent routine annual PPD screening and were identified by the Occupational Health Department as having a reaction of 10 to 14 mm to PPD.

Results:

Nineteen employees were identified as candidates and 11 underwent dual skin testing. Only 4 (36%) had repeat results for PPD in the 10- to 14-mm range, whether read by Occupational Health Department personnel or study investigators. For only 5 (45%) of the subjects did the Occupational Health Department personnel and study investigators concur (± 3 mm) on the size of the PPD reaction. Two of the 4 subjects with reactions of 10 to 14 mm as measured by the study investigators were M. avium sensitin dominant, 1 was PPD dominant, and 1 was nondominant.

Conclusion:

A reaction of 10 to 14 mm to PPD should not be used as an indication for the treatment of latent tuberculosis (TB) infection in healthy HCWs born in the United States with no known exposure to TB.

Optimistic expectancies and cell-mediated immunity: the role of positive affect

Optimistic expectancies affect many psychosocial outcomes and may also predict immune system changes and health, but the nature and mechanisms of any such physiological effects have not been identified. The present study related law-school expectancies to cell-mediated immunity (CMI), examining the within- and between-person components of this relationship and affective mediators. First-year law students (N = 124) completed questionnaire measures of expectancies and affect and received delayed-type hypersensitivity skin tests at five time points. A positive relationship between optimistic expectancies and CMI occurred: Changes in optimism correlated with changes in CMI. Likewise, changes in optimism predicted changes in positive and, to a lesser degree, negative affect, but the relationship between optimism and immunity was partially accounted for only by positive affect. This dynamic relationship between expectancies and immunity has positive implications for psychological interventions to improve health, particularly those that increase positive affect.

Gender differences in delayed-type hypersensitivity response: effects of stress and coping in first-year law students

Law students show significant deficits in emotional and physical well-being compared with groups of students in other areas of higher education. Furthermore, evidence suggests that these effects may be worse for women than for men. The use of active coping can positively affect immunity under stress, but this may be most true for men in the context of law school. The current study examined the delayed-type hypersensitivity (DTH) skin responses of first-year law students (n=121) and a comparison group (n=30). Students' health behaviors, self-evaluative emotions, and coping strategies were also reported. Male law students had larger DTH responses than females, but this gender effect was not present in the comparison group. Endorsement of perseverance under stress (n=19), an active coping strategy, moderated the gender effect on immunity. Perseverance associated with larger DTH responses and more positive self-evaluative emotion, but only among men. These results indicate that active coping may be less efficacious for women than for men in law school, which in turn may limit women's opportunities to attenuate negative effects of law school.

Social networks and immunosuppression during stress: relationship conflict or energy conservation?

Despite the apparent health benefits of social relationships, some studies indicate that larger social networks can be associated with greater vulnerability to infectious disease, particularly if stressors are also present. Two possibilities for such effects are, first, that more social contacts lead to more negative affect and social conflict during stressors, or second, that maintaining more social contacts is an energetically costly activity, and ecologically motivated immunosuppression is one means of providing energy to maintain social resources. First-year law students (N=76) completed questionnaires and had delayed-type hypersensitivity skin tests at five time points during their first 6 months of law school. Both moving away from home and a smaller social network associated with larger DTH responses (both p<0.05) across all time points. However, negative affect, either broadly defined or as specific affects (hostility, sadness, guilt), did not mediate social network effects, suggesting that negative affect and social conflict are less plausible explanations than ecological immunosuppression. Ecological models would predict that temporary immunosuppression is less harmful to health in the long run than loss of social resources.

How does optimism suppress immunity? Evaluation of three affective pathways

Studies have linked optimism to poorer immunity during difficult stressors. In this study, when 1st-year law students (N = 46) relocated to attend law school, reducing conflict among curricular and extracurricular goals, optimism predicted larger delayed-type hypersensitivity responses, indicating more robust in vivo cellular immunity. However, when students did not relocate, increasing goal conflict, optimism predicted smaller responses. Although this effect has been attributed to negative affect when difficult stressors violate optimistic expectancies, distress did not mediate optimism's effects on immunity. Alternative affective mediators related to engagement--engaged affect and fatigue--likewise failed to mediate optimism's effects, although all 3 types of affect independently influenced in vivo immunity. Alternative pathways include effort or self-regulatory depletion.

Interpretation of the tuberculin skin test reaction by pediatric providers

BACKGROUND

The tuberculin (TB) skin test is widely used, but it is not easy to read. There are few data on how well pediatric care providers interpret the TB skin test or on the success of various methods used to read the skin test reaction.

OBJECTIVE

To determine the ability of pediatric care providers to correctly read a positive TB skin test reaction and to identify the most successful method of measuring a TB skin test reaction.

METHODS

Twenty nurses, 16 staff pediatricians, 13 residents and 8 medical students who were working in a large pediatrics clinic were asked to read a 15-mm TB skin test reaction of a known converter. The study participants read the skin test using any technique they wished. The primary outcome measure was the percentage of providers who read the TB skin test as > or = 10 mm (considered a correct reading).

RESULTS

Seventy-seven percent (44 of 57) of the participants interpreted the TB skin test as > or = 10 mm, but 18% (10 of 57) of them read the skin test as negative (< or = 5 mm). The participants used a variety of interpretation techniques with 18 using the ballpoint pen technique. Participants who used the pen technique were significantly more likely to read the skin test as > or = 10 mm compared with those who used other methods (94% vs. 69%; P = 0.04). Pen technique users were also significantly less likely to measure the reaction as < or = 5 mm (0% vs. 26%; P = 0.02).

CONCLUSIONS

Many providers, regardless of professional training and experience, read a 15-mm TB skin test reaction as > or = 10 mm, but a significant minority interpreted it as negative. Use of the pen technique may decrease the number of false negative readings. Specific instruction on use of the pen technique to read TB skin tests should be incorporated into medical training curriculums.

Socially inhibited individuals show heightened DTH response during intense social engagement

To determine whether altered cellular immune response might mediate the increased health risks associated with social inhibition, we examined delayed type hypersensitivity (DTH) responses in 36 adults under conditions of low and high intensity social engagement. Participants come from a study of psychological factors in functional bowel disease and fibromyalgia. Under high engagement conditions, socially inhibited individuals showed significantly increased induration in response to intradermal tetanus toxoid. Under low engagement conditions, these individuals showed less pronounced DTH responses that did not differ in magnitude from those of uninhibited individuals. This pattern of results was found using two different measures of social inhibition and was independent of social inhibition's definition as a continuously distributed trait vs a discrete category. These data are consistent with the general hypothesis that social inhibition represents a predisposition to physiologic hyperresponsiveness that requires an exogenous social trigger for expression.

Modern approach to the diagnosis and treatment of tuberculosis in children

Tuberculosis in children remains an important infectious disease in the United States, with 1261 cases reported in 1985. The percentage of extrapulmonary manifestations is increasing. Advances in the diagnosis and treatment of tuberculosis in children have lagged behind those in adults owing to diminished familiarity with the disease and difficulty in performing clinical studies in children. Tuberculosis in the United States now occurs mainly in clusters of high-risk people, such as the foreign born, Hispanics, blacks, Native Americans, and the impoverished. In general, the diagnosis of tuberculosis is epidemiologic, supported by the chest roentgenogram, skin test, and, most important, contact tracing. As the rate of drug-resistant tuberculosis increases, greater effort should be made to obtain cultures. New advances, such as DNA probes and serodiagnosis, may improve diagnostic accuracy, especially for extrapulmonary tuberculosis. Noncompliance is the major problem in treating tuberculosis, and greater effort should be directed toward novel treatment approaches in children, such as twice-weekly supervised therapy and shorter, more intense durations of therapy.

A demonstration of lack of variability among six tuberculin skin test readers

The variability of tuberculin skin test readings among six trained and experienced readers was evaluated using a modified sliding caliper method. Each of 537 tests were read independently by two readers. There were 23 disagreements between paired readers resulting in an overall interobserver reliability of 95.7 per cent. In 82 per cent of the paired readings the results were different by 2 mm or less. The observer lack of variability was likely due to the training and experience of the readers.