Abstracts

Introduction

Tuberculosis (TB) remains the first cause of death from infectious disease worldwide ¹1. World Health Organization. Global tuberculosis report 2019. http://www.who.int/tb/publications/global_report/en/ (accessed on 15/Jan/2020).
http://www.who.int/tb/publications/globa... . Tuberculosis preventive therapy (TPT) is highly effective in individuals with latent tuberculosis infection (LTBI) ²2. World Health Organization. WHO consolidated guidelines on tuberculosis. Module 1: prevention. Geneva: World Health Organization; 2020., being the cornerstone for eliminating TB by 2050 ³3. Dye C, Glaziou P, Floyd K, Raviglione M. Prospects for tuberculosis elimination. Annu Rev Public Health 2013; 34:271-86.^,44. United Nations. Political declaration of the UN General Assembly High-Level Meeting. https://www.who.int/tb/unhlmonTBDeclaration.pdf (accessed on 17/Jan/2020).
https://www.who.int/tb/unhlmonTBDeclarat... . The many barriers at different steps of the cascade of care for LTBI, however, result in less than 30% of those eligible for TPT receiving a prescription and less than 19% completing treatment ⁵5. Alsdurf H, Hill PC, Matteelli A, Getahun H, Menzies D. The cascade of care in diagnosis and treatment of latent tuberculosis infection: a systematic review and meta-analysis. Lancet Infect Dis 2016; 16:1269-78.. The effect of TPT on public health remains thus minimal ¹1. World Health Organization. Global tuberculosis report 2019. http://www.who.int/tb/publications/global_report/en/ (accessed on 15/Jan/2020).
http://www.who.int/tb/publications/globa... , despite the inclusion of new shorter and safer TPT regimens by the World Health Organization (WHO) guidelines ²2. World Health Organization. WHO consolidated guidelines on tuberculosis. Module 1: prevention. Geneva: World Health Organization; 2020..

The risk of progression from LTBI to active disease is higher in those with a positive LTBI test, either the tuberculin skin test (TST) or interferon-gamma release assays (IGRA) ⁶6. Campbell JR, Winters N, Menzies D. Absolute risk of tuberculosis among untreated populations with a positive tuberculin skin test or interferon-gamma release assay result: systematic review and meta-analysis. BMJ 2020; 368:m549.. Not surprisingly, TPT has been shown to be more beneficial for those with a positive LTBI test ⁷7. Akolo C, Adetifa I, Shepperd S, Volmink J. Treatment of latent tuberculosis infection in HIV infected persons. Cochrane Database Syst Rev 2010; (1):CD000171.^,88. Smieja MJ, Marchetti CA, Cook DJ, Smaill FM. Isoniazid for preventing tuberculosis in non-HIV infected persons. Cochrane Database Syst Rev 2000; (2):CD001363.^,99. Samandari T, Agizew TB, Nyirenda S, Tedla Z, Sibanda T, Shang N, et al. 6-month versus 36-month isoniazid preventive treatment for tuberculosis in adults with HIV infection in Botswana: a randomised, double-blind, placebo-controlled trial. Lancet 2011; 377:1588-98.. Thus, TST (or IGRA, where available) is a mandatory test in the LTBI cascade of care, except for patients living with HIV (PLHIV) or for patients younger than five years old, who have a higher risk of progressing to active disease ²2. World Health Organization. WHO consolidated guidelines on tuberculosis. Module 1: prevention. Geneva: World Health Organization; 2020.. However, of the 30 million HIV-negative individuals five years of age or older that should receive TPT by 2022 ⁴4. United Nations. Political declaration of the UN General Assembly High-Level Meeting. https://www.who.int/tb/unhlmonTBDeclaration.pdf (accessed on 17/Jan/2020).
https://www.who.int/tb/unhlmonTBDeclarat... , 20 million require a positive LTBI test. TST is simple to perform, dispense with laboratory infrastructure and has good accuracy ¹⁰10. Trajman A, Steffen RE, Menzies D. Interferon-gamma release assays versus tuberculin skin testing for the diagnosis of latent tuberculosis infection: an overview of the evidence. Pulm Med 2013; 2013:601737.. Newer and more specific TST using recombinant tuberculin based on ESAT-6 and CP-10 proteins, have already been adopted in some BRICS countries ¹¹11. Abubakar I, Jackson C, Rangaka MX. C-Tb: a latent tuberculosis skin test for the 21st century? Lancet Respir Med 2017; 5:236-7.^,1212. Nikitina IY, Karpina NL, Kasimceva OV, Gergert VY, Ergeshov A, Lyadova IV. Comparative performance of QuantiFERON-TB Gold versus skin test with tuberculosis recombinant allergen (Diaskintest) among patients with suspected pulmonary tuberculosis in Russia. Int J Infect Dis 2019; 86:18-24.^,1313. Zellweger JP, Sotgiu G, Corradi M, Durando P. The diagnosis of latent tuberculosis infection (LTBI): currently available tests, future developments, and perspectives to eliminate tuberculosis (TB). Med Lav 2020; 111:170-83..

Despite being a simple test, reproducibility of induration readings has been reported to be low ¹⁴14. Ozuah PO, Burton W, Lerro KA, Rosenstock J, Mulvihill M. Assessing the validity of tuberculin skin test readings by trained professionals and patients. Chest 1999; 116:104-6.^,1515. Teruel JR, Ruffino Netto A, Duarte GG. Standardization of tuberculin test readers. Tubercle 1969; 50:350-5.^,1616. Goel D, Mantan M, Sethi GR. Mantoux test revisited: variability in reading tuberculin test in pediatric population. J Infect Dev Ctries 2018; 12:625-30.^,1717. Bearman JE, Kleinman H, Glyer VV, Lacroix OM. A study of variability in tuberculin test reading. Am Rev Respir Dis 1964; 90:913-9.. Thus, in some health systems, certification of healthcare workers for TST reading is needed, but specific requirements for certification vary widely ¹⁵15. Teruel JR, Ruffino Netto A, Duarte GG. Standardization of tuberculin test readers. Tubercle 1969; 50:350-5.. While ten TST applications and readings under the supervision of a certified professional are required for certification in Georgia, United States (https://dph.georgia.gov/sites/dph.georgia.gov/files/TB-TSTCertclass.pdf, accessed on 11/Sep/2020), Brazil has established 80 to 100 readings with 80% agreement with the trainer as a requirement ¹⁸18. Departamento de Vigilância das Doenças Transmissíveis, Secretaria de Vigilância em Saúde, Ministério da Saúde. Técnicas de aplicação e leitura da prova tuberculínica. Brasília: Ministério da Saúde; 2014.. Although protocols to train healthcare professionals for TST application and reading also vary widely, a control quality of TST performance based on a remote m-health method (mTST) has been reported as accurate, especially for readings under 5mm and over 14mm ¹⁹19. Moayedi-Nia S, Barss L, Oxlade O, Valiquette C, Ly M-X, Campbell JR, et al. The mTST - an mHealth approach for training and quality assurance of tuberculin skin test administration and reading. PLoS One 2019; 14:e0215240.. Based on this experience ¹⁹19. Moayedi-Nia S, Barss L, Oxlade O, Valiquette C, Ly M-X, Campbell JR, et al. The mTST - an mHealth approach for training and quality assurance of tuberculin skin test administration and reading. PLoS One 2019; 14:e0215240., we posited that a training protocol based on saline blebs simulation would be sufficient to certify healthcare professionals and tested this hypothesis.

Methods

From October 2019 to Jnauary 2020, we conducted an operational study in a primary care health unit in a high TB incidence favela in Rio de Janeiro, Brazil, setting chosen as to reduce the risk of multiple patients without any induration jeopardizing the evaluation step. Any healthcare professional or healthcare student was eligible to voluntarily participate in the training. We included all individuals who were available and agreed to participate by signing the informed consent form, and excluded those who had been previously trained. Based on reading variance reported in protocols from the 1960’s ¹⁵15. Teruel JR, Ruffino Netto A, Duarte GG. Standardization of tuberculin test readers. Tubercle 1969; 50:350-5., we established a sample of 40 trainees.

Trainees attended a 2-hour seminar on the importance of TPT and recommendations on how to identify contacts, apply, read, and interpret TST (adapted from Dick Menzies & Linette McElroy; Supplementary Material, http://cadernos.ensp.fiocruz.br/static//arquivo/suppl1-e00027321_5854.pdf), and watched a 7-minute demonstration video from the Brazilian Ministry of Health (available at https://www.youtube.com/watch?v=fRbg7vsa44o&t=4s). Following this theoretical introduction, the trainees participated in a reading training, where temporary blebs were produced by injecting 0.1mL of saline in sausages (simulating the intradermal technique; Supplementary Figure S1, http://cadernos.ensp.fiocruz.br/static//arquivo/suppl2-e00027321_9122.pdf). Finally, to simulate the Mantoux technique, we intradermally injected 0.1mL of saline in voluntary healthcare worker trainees, who signed a separate informed consent form. All blebs should have a minimum 6mm diameter and last 10 to 15 minutes, like the tuberculin bleb ²⁰20. Canadian Lung Association; Canadian Thoracic Society; Public Health Agency of Canada; Centre for Communicable Diseases and Infection Control. Canadian tuberculosis standards. https://central.bac-lac.gc.ca/.item?id=HP40-18-2014-eng&op=pdf&app=Library (accessed on 06/Apr/2021).
https://central.bac-lac.gc.ca/.item?id=H... . Readings of both the sausages and the arm blebs were individual, each student blinded to the other readings. All training steps were provided by an experienced LTBI physician (A.T.) with no TST certification or experience with TST reading, who underwent training with sausages and voluntary saline blebs in the previous year as preparation for two research projects ¹⁹19. Moayedi-Nia S, Barss L, Oxlade O, Valiquette C, Ly M-X, Campbell JR, et al. The mTST - an mHealth approach for training and quality assurance of tuberculin skin test administration and reading. PLoS One 2019; 14:e0215240.^,2121. Oxlade O, Trajman A, Benedetti A, Adjobimey M, Cook VJ, Fisher D, et al. Enhancing the public health impact of latent tuberculosis infection diagnosis and treatment (ACT4): protocol for a cluster randomised trial. BMJ Open 2019; 9:e025831.. The practical course lasted less than two hours, depending on the number of trainees attending. A schematic of the training process can be found in the Supplementary Figure S2 (http://cadernos.ensp.fiocruz.br/static//arquivo/suppl2-e00027321_9122.pdf).

To evaluate the effectiveness of this training, trainees underwent an evaluation step by reading TST indurations in service, which were compared to the reference standard of “true” induration readings by a trainer certified by the Brazilian Ministry of Health (90% concordance in 80-100 readings with a certified trainer). Both trainees and trainer were blinded to each other’s readings, and all readings (saline simulation and tuberculin induration) were performed using a caliper ruler (Supplementary Figure S3, http://cadernos.ensp.fiocruz.br/static//arquivo/suppl2-e00027321_9122.pdf).

Interobserver agreement was set at a difference up to 2mm between readings and analyzed using the Bland-Altman test ²²22. Bland JM, Altman DG. Agreement between methods of measurement with multiple observations per individual. J Biopharm Stat 2007; 17:571-82.. The trainee’s reading sensitivity and specificity and their 95% confidence intervals were calculated using 5mm and 10mm as cut-off points (measures used in Brazil, depending on the risk of progression to active TB and time since BCG vaccination) ²³23. Departamento de Vigilância das Doenças Transmissíveis, Secretaria de Vigilância em Saúde, Ministério da Saúde. Manual de recomendações para o controle da tuberculose no Brasil. 2ª Ed. Brasília: Ministério da Saúde; 2018.. To verify if the number of readings or the type of product injected (saline vs. tuberculin) had any significant effect on the agreement, we developed a linear mixed model with two hierarchical levels (per patient and per reader), including all readings (blebs and indurations), having as dependent variable the absolute difference between the trainees’ and trainer’s results in mm and as independent variables: the trainer’s readings, the number of readings and the type of product injected (saline or tuberculin). The model was considered robust if the mean residuals were close to zero. All analyses were performed in Stata (https://www.stata.com).

The study was approved by the Ethics Research Committee of the Anna Nery Nursing School/São Francisco de Assis Health Care Institute, Federal University of Rio de Janeiro (n. 3.256.347 on April 10, 2019) and by the Rio de Janeiro Health Secretariat (n. 3.470.316 on July 25, 2019). All patients and healthcare workers signed an informed consent form before participating in the study.

Results

Of the 64 eligible healthcare workers, 15 were available for training in three different sessions. Each trainee read an average of 6.8 (± 2.2) blebs in sausages and 3.5 (± 1.3) blebs in volunteers. Of the 15 participants, 11 were evaluated in service with an average of 14.7 (± 5.4) TST readings each. These included one pharmacist, two physicians, two registered nurses, two nursing assistants, and four community health agents with nursing assistant training. Overall, they performed 141 readings - 53 blebs and 88 indurations - before the project’s interruption due to the SARS-CoV-2 pandemic.

The Bland-Altman test found a high agreement for the 88 induration readings performed in 20 arms, with an average bias of 0.07mm and 94.3% of the plots within the 2s band (Figure 1). Sensitivity of the trainees’ readings was 100% (94.6%; 100.0%) at 5mm cut-off and 87.3% (75.5%; 94.7%) at 10mm cut-off, while specificities were 95.5% (77.2%; 99.9%) and 90.9% (75.7%; 98.1%), respectively. Supplementary Table S1 (http://cadernos.ensp.fiocruz.br/static//arquivo/suppl2-e00027321_9122.pdf) presents the interobserver agreement by range of the trainer’s reading.

As for the mixed regression model coefficients (Table 1), the number of readings had no significant effect on the agreement. Its coefficient was -0.0007, meaning that 131 readings (estimated by 1/0.0007) would be necessary to result in a 1mm difference between the trainees’ and trainer’s readings. Tuberculin resulted in a 0.9mm (estimated by 1/1.065) larger difference than saline. Finally, the larger the trainer’s reading, the greater the difference with the trainee’s (result consistent with the lower sensitivity for the 10mm cut-off). Since the mean residuals of the model were close to zero, it was considered robust.

Discussion

The simple protocol for TST reading training with saline simulations in an average of 3.5 volunteers presented here was sufficient to obtain a high agreement for TST induration readings, and a very high sensitivity for classifying patients into positive or negative results according to two different cut-off points (5mm and 10mm). The number of readings had no effect on the agreement. Overall, these findings suggest that training with very few saline blebs may be effective in certifying healthcare workers to read TST in service. This proposed protocol simplifies the logistics of training, is more ethically acceptable, and dispense with the need for highly experienced trainers.

Another of its advantages was training TST application, as incorrect administration of the technique was cited as a potential cause for false negative TST results ²⁰20. Canadian Lung Association; Canadian Thoracic Society; Public Health Agency of Canada; Centre for Communicable Diseases and Infection Control. Canadian tuberculosis standards. https://central.bac-lac.gc.ca/.item?id=HP40-18-2014-eng&op=pdf&app=Library (accessed on 06/Apr/2021).
https://central.bac-lac.gc.ca/.item?id=H... . An improvement to this protocol would be to add a step to evaluate the application and verify if the trainer can read the bleb size within 10 to 15 minutes, the usual duration ²⁰20. Canadian Lung Association; Canadian Thoracic Society; Public Health Agency of Canada; Centre for Communicable Diseases and Infection Control. Canadian tuberculosis standards. https://central.bac-lac.gc.ca/.item?id=HP40-18-2014-eng&op=pdf&app=Library (accessed on 06/Apr/2021).
https://central.bac-lac.gc.ca/.item?id=H... .

The literature also reports a high intra- and interobserver variability in TST reading ²⁴24. Kendig EL, Kirkpatrick BV, Carter WH, Hill FA, Caldwell K, Entwistle M. Underreading of the tuberculin skin test reaction. Chest 1998; 113:1175-7.^,2525. Pouchot J, Grasland A, Collet C, Coste J, Esdaile JM, Vinceneux P. Reliability of tuberculin skin test measurement. Ann Intern Med 1997; 126:210-4.^,2626. Longfield JN, Margileth AM, Golden SM, Lazoritz S, Bohan JS, Cruess DF. Interobserver and method variability in tuberculin skin testing. Pediatr Infect Dis 1984; 3:323-6., with greater differences in readings, especially when these approach positivity cut-off points ¹⁶16. Goel D, Mantan M, Sethi GR. Mantoux test revisited: variability in reading tuberculin test in pediatric population. J Infect Dev Ctries 2018; 12:625-30.. Since a 2mm difference, for example, represents 50% on a 4mm result and only 20% on a 10mm result, more errors are expected with larger readings. Larger readings could also be expected with tuberculin as the caliper ruler squeezes the bleb, which is not observed with induration. A well-conducted study comparing intra- and interobserver readings using a pair of calipers and a transparent ruler, however, showed that the variability between TST induration readings is not influenced by changing the reading instrument ²⁷27. Geldenhuys H, Verver S, Surtie S, Hatherill M, van Leth F, Kafaar F, et al. The tuberculin skin test: a comparison of ruler and calliper readings. Int J Tuberc Lung Dis 2010; 14:1266-71..

TST is the most widely LTBI test available and despite its limitations, the test has good accuracy, does not require laboratory facilities, and is simple to perform and interpret ¹⁹19. Moayedi-Nia S, Barss L, Oxlade O, Valiquette C, Ly M-X, Campbell JR, et al. The mTST - an mHealth approach for training and quality assurance of tuberculin skin test administration and reading. PLoS One 2019; 14:e0215240.; any healthcare professional skilled in performing intradermal vaccines, as BCG, is able to inject the tuberculin. TST reading, however, has been subject to complex protocols that require a certified trainer and the availability of several voluntary arms, thus hampering its wide availability in public healthcare systems. Our findings have relevant pragmatic implications. Our protocol is also safer and more ethically acceptable. Tuberculin injection, although generally well tolerated, can cause local adverse reactions such as itching, pain, blistering, a necrotic reaction and vagal malaise ²⁸28. Christopher DJ, Shankar D, Datey A, Zwerling A, Pai M. Safety of the two-step tuberculin skin test in Indian health care workers. Int J Mycobacteriol 2014; 3:247-51.. Saline injection is safe despite mild temporary local discomfort, usually a burning sensation. An alternative method to avoid training on human arms is to use artificial arm models, but evaluating the effectiveness of such method was beyond the scope of the present study.

Our study has a few limitations. First, generalizability is difficult from the small sample of a single healthcare unit. Second, this small sample size does not allow for stratified analyses by professional background as other studies have done with the ability of paramedics ²⁹29. Haynes BE, Grubb R. Paramedics can apply and read Mantoux tuberculosis tests. J Emerg Med 2001; 20:381-4., pharmacists and other healthcare workers ³⁰30. Jakeman B, Gross B, Fortune D, Babb S, Tinker D, Bachyrycz A. Evaluation of a pharmacist-performed tuberculosis testing initiative in New Mexico. J Am Pharm Assoc (2003) 2015; 55:307-12.^,3131. Howard TP, Solomon DA. Reading the tuberculin skin test: who, when, and how? Arch Intern Med 1988; 148:2457-9. to read TST. However, the overall performance of our participants was very good, suggesting that being able to read TST does not depend on professional background. Finally, we did not evaluate different reading techniques ³²32. Morán-Mendoza O, Tello-Zavala MC, Rivera-Camarillo M, Ríos-Meza Y. Comparison of different methods and times for reading the tuberculin skin test. Int J Tuberc Lung Dis 2013; 17:1273-8..

Our study also has strengths, such as the in-service evaluation carried out by a certified trainer and both trainees and trainers being blinded for the readings. Also, different analyses attest to the robustness of the findings.

In summary, the simple and realistic training protocol successfully evaluated in this study may reverse the scenario of unavailability of certified personnel in LTBI cascade of care, situation created by complex certifications ³³33. Salame FM, Ferreira MD, Belo MT, Teixeira EG, Cordeiro-Santos M, Ximenes RA, et al. Knowledge about tuberculosis transmission and prevention and perceptions of health service utilization among index cases and contacts in Brazil: understanding losses in the latent tuberculosis cascade of care. PLoS One 2017; 12:e0184061.. As new and more specific TST are developed ¹¹11. Abubakar I, Jackson C, Rangaka MX. C-Tb: a latent tuberculosis skin test for the 21st century? Lancet Respir Med 2017; 5:236-7.^,1212. Nikitina IY, Karpina NL, Kasimceva OV, Gergert VY, Ergeshov A, Lyadova IV. Comparative performance of QuantiFERON-TB Gold versus skin test with tuberculosis recombinant allergen (Diaskintest) among patients with suspected pulmonary tuberculosis in Russia. Int J Infect Dis 2019; 86:18-24.^,1313. Zellweger JP, Sotgiu G, Corradi M, Durando P. The diagnosis of latent tuberculosis infection (LTBI): currently available tests, future developments, and perspectives to eliminate tuberculosis (TB). Med Lav 2020; 111:170-83., TST reading will remain a necessity.

Acknowledgments

We would like to thank the participants and healthcare managers of the clinic, Dr. Dick Menzies (McGill University, Montreal, Canada), and Linette McElroy (TB training and resource consultant, Victoria, Canada), for training two authors and providing the training material. A.T. received a grant by the Brazilian National Reseach Council (CNPq), and M.L.B. by the Canadian Institutes of Health Research (CIHR). The funding sources have no responsibility on the study conducted or the statements disclosed in this manuscript.

References

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