Page 627 - TNFlipTest

Toronto Notes 2019 HIV and AIDS
Investigations
• screeningforlatentTBmaybedoneviatuberculinskintest(TST)orIFN-γreleaseassay(IGRA)
■ both can be used to diagnose prior TB exposure. IGRA has fewer false positives as does not detect
antigens in BCG vaccine or most types of non-tuberculosis-Mycobacteria
◆ neither should be used for active TB diagnosis or monitoring anti-TB treatment response
◆ TST preferred when repeat testing planned to assess risk of new infection (e.g. serial testing in
healthcare)
■ IGRA preferred when BCG vaccine after 1 year of age, vaccination more than once, or unable to
return for reading
• diagnostictests/investigationsforactivepulmonaryTB
■ sputum specimens (either spontaneous or induced) should be collected for acid-fast bacilli smear and culture; the three specimens can be collected on the same day, a minimum of 1 hour apart
■ BAL if other lung pathology (ex. lung cancer) also suspected, or TB suspected despite negative sputum samples
■ CXR
◆ classic triad: apical-posterior infiltrates, lung volume loss, cavitation
◆ atypical features: hilar/mediastinal lymphadenopathy, non-cavitary infiltrates
◆ signs of complications: endobronchial spread, pleural effusion, pneumothorax
◆ ghon complex: a parenchymal granuloma, indicating a previous tuberculosis infection, and an
involved hilar lymph node on the same side
Prevention
• primaryprevention
■ airborne isolation for active pulmonary disease ■ BCGvaccine
◆ ~80% effective against pediatric miliary and meningeal TB
◆ effectiveness in adults debated (anywhere from 0-80%)
◆ recommended in high-incidence communities in Canada for infants in whom there is no
evidence of HIV infection or immunodeficiency; widely used in other countries • secondaryprevention(deferinpregnancyunlessmotherishighrisk)
■ likely INH-sensitive: isoniazid (INH) + pyridoxine (vitamin B6 to help prevent INH-associated neuropathy) x 9 mo
■ likely INH-resistant: rifampin x 4 mo and referral to ID physician specializing in TB
Treatment of Active Infection
• giventhenuancesofTBtreatment,activeTBinfectionshouldbemanagedbyanexperiencedTB clinician
• pulmonaryTB:INH+rifampin+pyrazinamide+ethambutolx2mo(initiationphase),thenINH+ rifampin x 4 mo in fully susceptible TB (continuation phase), total 6 mo. Extend continuation phase to 7 months if age >65, pregnant or risk of hepatotoxicity
• extrapulmonaryTB:sameregimenaspulmonaryTBbutincreaseto12moinbone/joint,CNS,and miliary/disseminated TB + corticosteroids for meningitis, pericarditis
• empirictreatmentofsuspectedMDR(multidrugresistant)orXDR(extensivelydrug-resistant)TB requires referral to a specialist
■ MDR=resistancetoINHandrifampin±others
■ XDR = resistance to INH + rifampin + fluoroquinolone + ≥1 of injectable, second-line agents
• verydifficulttotreat,globalpublichealththreat,5documentedcasesinCanadafrom1997-2008
■ suspect MDR TB if previous treatment, exposure to known MDR index case, or immigration from a high-risk area
• note:TBisareportablediseasetoPublicHealth(pleaseseePublicHealthAgencyofCanadawebsitefor more information)
HIV and AIDS
Epidemiology
Canadian Situation (Public Health Agency of Canada, 2016)
• estimated65,040CanadianslivingwithHIVinfectionattheendof2016,20%unawareofHIV-positive status
• 2,090newinfectionswerereportedin2013:MSMaccountfor53%ofcases,IDU19%
Global Situation (WHO and UNAIDS Core Epidemiology Slides, July 2018)
• estimated36.7millionpeoplelivingwithHIV/AIDSattheendof2016 • estimated1.8millionnewlyinfectedin2016
• estimated1millionAIDS-relateddeathsin2016
Infectious Diseases ID27
Positive TST Test
If induration at 48-72 h
>5 mm if immunocompromised, close contact with active TB
>10 mm all others; positive PPD → CXR; decision to treat depends on individual risk factors
False(–): poor technique, anergy, immunosuppression, infection <10 wk or remotely
False(+): BCG after 12 mo of age in a low- risk individual, NTM
Booster effect: initially false(–) result boost to a true(+) result by the testing procedure itself (usually if patient was infected long ago so had diminished delayed type hypersensitivity reaction or if history of BCG)