TB Infection Control: Fears and Facts Lisa V. Adams, MD Elizabeth A. Talbot, MD Dartmouth Medical School June 2011
Outline Background Warm-up with easy myth busting Challenge round myth busting Your participation will make or break it! At least jot your answer if not call it out.
Background: TB is important, interesting and infectious
Transmission of M. tuberculosis Spread by airborne route Droplet nuclei 1-5um Transmission affected by Infectiousness of patient Environmental conditions Duration of exposure Most exposed persons do not become infected; most infected persons do not become diseased
First Interventions to Prevent Transmission 1882 Koch recognized TB is caused by transmissible bacteria Led to strategies to prevent 1880: TB reportable 1900: TB programs Screening and isolation Dedicated campaigns to improve personal hygiene Curb public spitting
Sanatoria: Clear Public Gains Sanatoria: 50% of those who entered were dead within 5 years TB untreated Contribution was preventing TB transmission In Europe 1850-1950 (absence of treatment and AII), deaths from TB fell from 500 to 50 per 100,000 population Improvements in infection control and public health reduced TB
Mythbusters: TB Infectiousness Warm-up Round
Vignette #1 Attempting to follow your (low TB risk) hospital s TB Control Policy, when a new hire declines TST She is 28 weeks into a high risk pregnancy Her OB supports her concern for potential ill effects on her fetus from PPD
TB Testing Frequency Risk classification Low Medium Potential ongoing transmission Frequency Baseline on hire; further testing not needed unless exposure occurs Baseline, then annually Baseline, then every 8 10 wks until evidence of transmission has ceased MMWR 2005; 54 (No. RR-17): 1 141
Truth or Myth? Pregnant HCWs* should be exempted from baseline, serial and/or exposurerelated TSTs** until after delivery. *healthcare workers **tuberculin skin test
Guidelines for Preventing Transmission of M.tb in Health- Care Settings, 2005 No evidence that TST has any adverse effects on pregnant mother or fetus Pregnant HCWs should be included in serial skin testing No contraindications Postponing diagnosis of LTBI during pregnancy is unacceptable MMWR 2005; 54 (No. RR-17): 1 141
Truth or Myth? Pregnant HCWs should be exempted from baseline, serial and/or exposurerelated TSTs until after delivery.
Vignette #2 You are called to resolve a conflict between medical and nursing staff 76 yo patient moved from China 10 years ago is about to have chemotherapy for CLL TST was ordered and planted Nursing staff initiates transfer to AII*, but her attending refuses *Airborne Infection Isolation
Truth or Myth? Any inpatient for which a clinician orders TST/IGRA should be on Airborne Infection Isolation.
Expert Opinion Evaluation for LTBI* (TST/IGRA) may be done unrelated to risk of current infectious active TB Our bias: TST/IGRAs are not part of routine workup for TB AFB smear is! TST/IGRA only helpful for TB disease when positive and patient is from low incidence setting Find out indication for TST/IGRA *latent TB infection
Truth or Myth? Any inpatient for which a clinician orders TST/IGRA should be on Airborne Infection Isolation.
One Month Later... 76 yo patient moved from Mexico 30 years ago, received CLL chemo 2 mos ago, admitted for 1 month cough TST had been 0mm CT shows nodules and small cavities 3 AFB smears/cultures ordered Nursing staff initiates transfer to AII, but her attending refuses
Truth or Myth? Any inpatient for which a clinician orders AFB smear should be on Airborne Infection Isolation.
Additional Information This patient was known to have M. avium pulmonary disease AFB smears can be used to diagnose and monitor nontuberculosis mycobacterial (NTM) pulmonary infections Find out indication for AFB smear
Truth or Myth? Any inpatient for which a clinician orders AFB smear should be on Airborne Infection Isolation.
Wait a Minute... All 3 smears are numerous positive Probe confirms M. avium complex, no M. tb complex Shouldn t this patient (on hematology / oncology ward) still be transferred to AII?
Truth or Myth? Airborne infection isolation is indicated for a patient with cavitary M. avium disease.
Human NTM* Infections NTM can cause pulmonary, cutaneous, disseminated or lymphatic disease No human-to-human transmission No need for AII!! M. avium complex (MAC) especially Localized cervical adenitis age 1-5 Disseminated disease in AIDS Localized pulmonary disease in adults Mimics TB, but slower and less virulent than TB *Nontuberculous mycobacteria
Truth or Myth? Airborne isolation is indicated for a patient with cavitary M. avium disease.
Mythbusting Challenge Round
Vignette #3 25 yo W Sierra Leone refugee outpatient with noncavitary pulmonary TB Minimal radiographic abnormalities 7/7 neg AFB smears on good sputa, Cx pos Infrequent or no cough Her family/social circles very resistant to testing PCP does not think contact investigation warranted
Truth or Myth? Only patients with AFB smear positive sputum transmit TB.
The Evidence Smear pos TB most infectious Smear-neg, culture-pos TB index cases found to be responsible for some transmission Molecular epidemiologic studies show 17% of TB transmission in San Francisco study* 13% of TB transmission in the Netherlands** *Behr. Lancet 1999; 353: 444 **Tostman. CID 2008; 1135
CDC Contact Investigation Guidelines* Decision to initiate contact investigation based on 1. Anatomic site Only pts with pulmonary, pleural and laryngeal TB transmit naturally Autopsy, abscess irrigation can transmit 2. Smear and culture positive BAL and bronch wash same as expectorated? 3. Cavities on CXR Cavities only on CT less compelling 4. Age *MMWR 2005;54 (No. RR-15)
Truth or Myth? Only patients with AFB smear positive sputum transmit TB.
Vignette #4 March 2007 American lawyer thought to have XDR TB* Disregarded warnings not to travel and boarded several international flights Hundreds of passengers exposed Case raised urgent issues regarding Strength of govt isolation authority Airline travel offers simplified spread of TB *Extensively drug resistant TB
Truth or Myth? TB is easily transmitted on airplanes.
The Evidence No case of clinical or bacteriologically-confirmed TB disease associated with exposure during air travel has been identified Risk of transmission of M. tuberculosis on board aircraft is low and limited to persons in close contact with infectious case for >8 hours Risk of infection is related to Infectiousness of the person with TB Susceptibility of those exposed Duration of exposure Proximity to the source case Efficiency of cabin ventilation WHO/HTM/TB/2008.399
The Guidelines If infectious patient was passenger on commercial flight <3 months before and flight >8 hours: Public health authority, in cooperation with the airline company, gathers contact details of passengers sitting in the same row and in the two rows in front of and behind the TB case No contact investigation if infectious patient was crew member Crew members not considered contacts
Truth or Myth? TB CAN be transmitted on airplanes (but there are clear guidelines to identify those who are at risk for TB infection).
Vignette #5 27 yo W from Liberia with noncavitary drug sensitive TB has been on AII, tolerating effective therapy, with improvement in cough, fevers At 2 weeks, 3 AFB smears have gone from 4+ to 3+ She wants to go home
Truth or Myth? All AFB smear positive patients are infectious and should be maintained in airborne infection isolation.
Arguments for Early Removal from Isolation Retrospective study of Household Contacts (HHCs) in India* Group A: 86 cx+ (52 sm+) patients discharged before smear converted Group B: 69 both cx- and sm- at discharge No differences in infection of HHC BUT median hospital days 38 (A) and 36 (B) 21 (20 sm+) patients discharged after mean of 15 days No conversions among 72 TST-neg HHCs** *Brooks SM. Am Rev Respir Dis 1973; 108:799-804 **Gunnels JJ. Am Rev Respir Dis 1974; 109:323-30
Limitations of Data Most epidemiology based on discharge after >2 weeks of inpatient treatment India study limited by high background Those most susceptible or exposed were probably already infected But cough aerosol data suggests rapid decrease of viable airborne bacilli from patients during treatment* *Fennelly. AJRRCM 2004; 169:604-9
Discharge to Home Isolation (without 3 negative smears) if: Follow-up plan with local TB program Patient is on standard treatment and directly observed therapy (DOT) is arranged Clinically improving with improvement in smear grade Low suspicion of MDR-TB
Discharge to Home Isolation (Without 3 negative smears) if: No person in home <4 years old Immunocompromised All in household previously exposed Patient willing to stay home until sputum results negative
Truth or Myth? All AFB smear positive patients are infectious and should be maintained in airborne infection isolation.
Bonus Vignette: From the mouths of babes 36 y o female guardian diagnosed with tuberculous arthritis of L hip 9 y o HHC diagnosed with PTB Is a contact investigation in his school indicated?
Truth or Myth? Children don t transmit TB.
Additional Info and Evidence 9 y o had extensive bilat cavitary disease* Smears 4+ 3/4 HHCs with TB disease, 4 th with LTBI 79% of 24 school contacts TST+ 34% of 32 school bus contacts TST+ Overall: 23% of all contacts TST+ 15 y o high school student with PTB** 10% of 559 school contacts TST+ 19% of 67 school bus contacts TST+ Adult-type transmission, Dx delayed *Curtis et al. NEJM, 1999. **Phillips et al. Pediatrics, 2004.
Truth or Myth? Children don t transmit TB. Initiating a contact investigation for a child with TB should be done in In consultation with area experts on a case by case basis.
Final Bonus Vignette: BCG Vaccination 39 y o from Serbia has a TST done as pre-employment for a daycare center Read as 19mm induration Patient adamant they cannot have TB because they received BCG vaccination as child and attributes the +TST to BCG
Truth or Myth? BCG vaccination provides lifelong protection
BCG Vaccination BCG provides 80% protection during the first 2 years of life esp against miliary TB and TB meningitis BCG protection wanes over time Consensus: no protection provided in adulthood TST reaction induced by BCG also wanes over time, by age 15 ~ no effect Ignore history of BCG when interpreting TST and recognize protection likely has waned Colditz et al, JAMA 1994, Colditz et al. Pediatics 1995.
Truth or Myth? BCG vaccination provides lifelong protection
THANKS FOR YOUR ATTENTION!