tuberculin skin test

tuberculin skin test
Greg Knobloch · Public domain · source
Name	Tuberculin skin test
Specialty	Infectious disease, Pulmonology

tuberculin skin test

The tuberculin skin test is a diagnostic procedure used to detect immune sensitization to mycobacterial antigens, primarily in the context of Robert Koch's discovery of the tubercle bacillus and subsequent public health responses such as the Bacillus Calmette–Guérin vaccine introduction. Developed amid early 20th-century efforts led by figures like Charles Mantoux and institutions including the Pasteur Institute and the Rockefeller Foundation, the test has been incorporated into screening programmes by agencies such as the World Health Organization and national bodies like the Centers for Disease Control and Prevention.

Introduction

The test involves intradermal injection of a standardized purified protein derivative (PPD) preparation derived from Mycobacterium tuberculosis cultured by laboratories influenced by methods from the Institut Pasteur and pharmaceutical manufacturers with ties to the Wellcome Trust era. Historically, proponents including Robert Koch and critics such as investigators from the Royal Society debated tuberculin utility during public health campaigns in cities like London and New York City. Large-scale applications intersected with public health programmes tied to leaders like Florence Nightingale and policy initiatives from the League of Nations' health committees before modern adoption by the United Nations' successor agencies.

Indications and contraindications

Indications include screening of high-risk cohorts identified by public health authorities — for example, contacts of active tuberculosis cases traced by teams modeled after work from John Snow's epidemiologic investigations, employees in institutions such as Broadmoor Hospital-type psychiatric facilities, residents of congregate settings like Alcatraz Island-style prisons, and healthcare workers affiliated with hospitals akin to Mayo Clinic or Johns Hopkins Hospital. Pre-employment, pre-immigration, and pre-immunosuppression assessments (e.g., prior to therapies developed at institutions like Karolinska Institutet or Memorial Sloan Kettering Cancer Center) are typical. Contraindications include known severe hypersensitivity to PPD components, recent extensive burns or widespread dermatitis at the proposed injection site (clinical settings mirroring cases reported at institutions like Cleveland Clinic), and some recommendations avoid testing during acute febrile illnesses observed in outbreaks such as the 1918 influenza pandemic.

Procedure and technique

The classic Mantoux technique is performed with a sterile syringe and a 27–30 gauge needle, delivering 0.1 mL of PPD intradermally into the volar surface of the forearm, a method standardized in guidelines from agencies like the World Health Organization, Centers for Disease Control and Prevention, and national authorities analogous to the National Health Service (England). Trained clinicians educated in protocols from medical schools such as Harvard Medical School, University of Oxford, or UCLA perform and measure the resulting induration 48–72 hours later, recording transverse diameter in millimeters as practiced in clinical trials registered with regulators like the Food and Drug Administration or reported in journals associated with the Royal College of Physicians. Proper aseptic techniques and documentation follow frameworks from organizations including the American Medical Association.

Interpretation and criteria for positivity

Interpretation uses size thresholds tailored to risk categories established by bodies such as the Centers for Disease Control and Prevention, Public Health England, and national advisory committees similar to the Advisory Committee on Immunization Practices. Typical cutoffs include indurations ≥5 mm for recent contacts of active cases and immunocompromised patients managed at centers like St Bartholomew's Hospital, ≥10 mm for recent immigrants from high-prevalence regions listed by the World Health Organization and residents of high-risk settings including facilities like Rikers Island, and ≥15 mm for individuals without known risk factors per recommendations from public health authorities in countries such as Canada and Australia. Documentation often references cohort studies published by researchers affiliated with institutions like Imperial College London and Johns Hopkins Bloomberg School of Public Health.

Sensitivity, specificity, and limitations

Sensitivity and specificity vary with host factors, prior immunization with Bacillus Calmette–Guérin, and cross-reactivity with environmental mycobacteria first described in fieldwork by investigators from agencies like the United States Public Health Service. False-negative results occur in anergic states seen in patients treated at centers such as MD Anderson Cancer Center or in severe illnesses like malnutrition crises addressed historically by Red Cross relief efforts. False-positive reactions are common in BCG-vaccinated populations from countries such as India, Japan, and Brazil where public health programmes implemented widespread immunization. Meta-analyses published in journals connected to publishers like Elsevier and Springer highlight variable predictive values influenced by pretest probability, paralleling methodological discussions from statisticians associated with institutions like London School of Hygiene & Tropical Medicine.

Adverse reactions and complications

Local reactions range from mild erythema and pruritus to larger inflammatory responses occasionally managed in outpatient clinics affiliated with hospitals like Guy's Hospital; rare complications include extensive necrosis, ulceration, or blistering requiring care analogous to wound management at St Thomas' Hospital. Hypersensitivity reactions and keloid formation have been reported in susceptible individuals from dermatology clinics associated with universities like University of California, San Francisco. Systemic allergic reactions are rare but necessitate emergency protocols comparable to those recommended by the American Heart Association for anaphylaxis management.

Comparison with interferon-gamma release assays

Interferon-gamma release assays (IGRAs), developed through collaborations between biotechnology firms and research groups similar to those at Pasteur Institute and Imperial College London, measure T-cell release of interferon-gamma in response to specific Mycobacterium tuberculosis antigens absent from BCG strains, reducing cross-reactivity noted in populations studied in countries such as South Africa and China. IGRAs, marketed by companies like those that brought forward diagnostics at Roche or Qiagen-partnered units, offer logistical advantages including single-visit testing and standardized laboratory automation used in reference labs such as those at Mayo Clinic Laboratories, but they require phlebotomy and laboratory infrastructure comparable to facilities at Karolinska Universitetssjukhuset. Comparative effectiveness research from academic centers such as Johns Hopkins and University of Toronto shows trade-offs in cost, accessibility, and performance that shape national policies from agencies like Public Health Agency of Canada and NHS England.

Category:Medical tests