Surveillance for latent tuberculosis in the Workplace: Pitfalls of Screening Low Risk Workers Disclosure page l I have nothing to disclose l Pictures came from WikiMedia Commons Thomas E. Gamsky, MD, MPH Public Domain Medical Director l Some slides Include images of victims of Contra Costa County tuberculosis to rescue you from looking at Vista Oaks Occupational Medicine [Employee too many slides of TB data Occupational Medicine l Opinions expressed are my own, and Clinic] represent my perspective as an Friday March 9 th 2018 occupational medicine provider for 28 years Definition of “pitfall” [Google Why screen asymptomatic persons for dictionary] latent tuberculosis [TB]? TB is the leading cause of l pit·fall 1. death from infectious l /ˈpitˌfôl/ disease worldwide; TB l noun: pitfall; plural noun: pitfalls caused massive epidemics in the past centuries l a hidden or unsuspected danger or difficulty. Now kills 1.8 mill/year 2. l synonyms: hazard, danger, risk, peril, difficulty, worldwide: also disables catch, snag, stumbling block, drawback 1/3 of the world’s 3. l "home schooling has its pitfalls" population is infected There is a real potential of 4. recurrent epidemics from reactivation of latent dz 1
Evolving definition of Screening versus Diagnostic “Latent tuberculosis infection” definition (I) Testing for Latent TB [2016 US Preventative Services [Center for Disease Control (CDC) 2013] Task Force] l Screening is an evaluation l “The presence of Mycobacterium tuberculosis in the of asymptomatic persons body without signs and symptoms, or radiographic or for the purpose of bacteriologic evidence of tuberculosis (TB) disease.” identifying candidates for l “Detected by” IGRA or TST medication to prevent l Once the decision has been made to test, latent TB is progression to active TB defined by diagnostic test results. No corroborating l Diagnostic testing is signs or symptoms and no confirmatory diagnostic administering a Tuberculin skin test (TST) tests of higher accuracy are required. or Interferon-gamma l “The intention to test should be a targeted intention release assay (IGRA) for to trust and treat the result” [van Zyl –Smit 2015] screening purposes 2017 Clinical Practice Guidelines made important CDC definition of Latent tuberculosis is not changes for the diagnosis of latent TB in low risk related to pretest probability settings [American Thoracic Society/CDC]: l This definition does not take into account the pre-test l Recommend low risk persons not be tested probability of TB disease. l For low risk persons: Suggest a second diagnostic test l Almost half of all counties in California had no TB in [either an IGRA or a TST] if the initial test is positive 2016 [> 1/3 of counties had no TB in 10 years] (however the evidence is “very low” for this recommendation) Yet a nurse who works in Amador County, which has no reported TB cases in the last 10 years, could be l Infection is diagnosed if both tests are positive considered to have latent TB if their mandatory annual l The actual risk of TB disease, or the probability that a testing was positive in the absence of any TB exposure, positive result is truly positive is still not factored into even though the false positive rate of the screening test is this diagnostic algorithm known to be 3%. l Medium and low risk are not defined in this document. l A potential pitfall of screening low risk workers is l Providers may not know which workers are “low risk” diagnostic error during serial testing. 2
What type of worker is “low risk”? I: CDC [MMWR What type of HCW is “low risk”? II: CDC also 2005] defines Health Care Worker (HCW) risk defines low risk by setting: according to risk of exposure l Low risk: … applied to HCWs who will never be l Low risk: …settings in which persons with TB disease are exposed to persons with TB disease…. not expected to be encountered, and therefore exposure to M. tuberculosis is unlikely… a low risk hospital setting has l Medium risk: …HCW will or will possibly be less than 6 persons with TB disease in the last year for a exposed to persons with TB disease… hospital with > 200 beds in the preceding year. l Many providers feel all HCW with patient contact l Low risk outpatient/small hospital settings: exposure to <3 are medium risk by this criteria. persons with TB in the preceding year. l Therefore another potential pitfall for providers is l A HCW in a large hospital taking care of 5 TB patients in assigning the appropriate risk category for tested one year may be low risk by settings criteria but medium risk by exposure criteria workers. l Providers may be confused by the settings risk vs. exposure risk categories. The rationale for annual testing of all low risk HCW in Possible reasons NOT to test all low risk HCW annually I. California [CA] involves the concept that annual testing [California Department of Public Health (CDPH) 2016 and provides the most protection due to: Contra Costa County Dept Public Health]: l Dx of early infection; annual l Incidence of TB is low testing may identify (Number of TB cases in seroconversions earlier than County dropped from 105 in other protocols 2001 to 40 in 2016) Detection of infection in the l absence of a source l Scant longitudinal data for l CA has higher rates of TB than interpreting serial testing the US and needs more testing results l CDC HCW risk classification may l Limited information not be accurate due to unrecognized exposure to regarding how to interpret infected persons conflicting results when l [Vivian Leigh] more than one test is performed 3
Possible reasons not to test all low risk HCW Possible reasons not to test all low risk HCW annually III: annually, II: Risk of occupational transmission Risk of TB in HCW in CA is not elevated [CDPH 2015, may be quite low: Crowder et al 2018, unpublished] l Rates of TB in HCW were not l Youakim 2016, British Columbia: higher than non-HCW [RR: 0.84 found only 8 cases of (95% CI: 0.71-1.0) occupational TB in 10 years of l In 2016 there were 80 cases of testing (2 million workers); No TB in HCW in CA [1.4 mill. HCW] risk for first responders was found l 85% of these were foreign borne l [Pederson, 2016], Denmark: and likely infected outside of US found only 27 cases were likely l Rate of TB in foreign borne occupational in 21 years of HCW is 74 times that of US- annual HCW testing . borne (95% CI:43-129) l Rates of occupational TB in CA l [Rene Laennec] are unknown but likely very low Possible reasons not to test low risk HCW annually, Possible reasons not to test all low risk HCW annually, V. IV. Apparently RANDOM false positive QuantiFERON Apparently NONRANDOM positive QFT results could be –TB (QFT) results could be caused by: caused by: l Nontuberculous mycobacteria infection l Tube defects [e.g. endotoxin [Henderson 2012, Hermansen 2014, Hur contamination; Gamsky 2008, 2014] Slater 2012, Couturier 2014, Seto l The ESAT-6 and CFP-10 antigens used 2016, Igari 2017, FDA 2016] in IGRAs are also found in other l Handling/processing problems: nontuberculous mycobacterium and blood draw, tube handling after can cross react [van Pittius 2001, Arend draw, incubation [Pai 2014, 2005, Vordermeier 2007] Banaei 2016] l Immune boosting by the TST [Igari 2007, l Analytical/data entry error Perry 2008, Baker 2009] l Skin contaminants [Banaei 2016, l Persons drawn multiple times using Gaur 2014] unrecognized contaminated tube lots 4
Nevertheless, annual testing of all HCWs, emergency Case presentation: First Responder latent responders and paramedics in California is required by tuberculosis testing program 2000-2017 state law [CDPH Jan 2018] l California Code of l Contra Costa County has been regulations (8 CCR 5199), testing first responders since subsection 5199(h)(3) 1970s with Tuberculin Skin Test Airborne Transmissible Disease (ATD) Act. l In 2007 testing changed to QFT-TB-Gold and 2008 QFT- l CCR Title 22, Div. 5, Ch.1- Gold-In-Tube 12: requires most HCW to have annual TB l This cohort is low risk screenings (with a TB test if their prior result was negative), l [Henry VII England] County first responders are “Low risk” due to: Case study: Mr. A l The low County rate of TB disease [3.5 l First Responder x 5 years [US born] cases/100,000/year in 2016] l No BCG, no symptoms l The predominant “ US-born” nature of cohort l No exposure to tuberculosis or to persons l No persons known to be Bacillus Calmette-Guerin with an unidentified illness or cough [BCG] immunized l No known occupational cases of TB disease l Prior to this exam he had yearly negative l No known occupational TB exposure 2000-2017 TST (zero mm) x 4; negative x-ray; He had l No TST conversion from negative to positive from no TST the year before. 2000-2017 l This essentially meets low risk CDC settings criteria 5
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