Tuberculosis

Epidemilogy

- tb resurfaced due to poor public health systems, HIV, and immigration

- rate of tb now declining due to better public health and decrease xmission of tb from pt with active tb

- many people with latent tb- poses threat if turns active

- globally, 1/3 of world pop infcted

Consequences

- xmited by air particles 1-5 microns

- xmission influenced by source criteria- number of bacteria excreted and nature of encounter

- infc by 1- 5 bacteria in terminal alveolus

- primary tb usually mild and self limited- often undiagnosed- bacteria seed other organs for subsequent reactivation later

- 5% of time, infc goes from latent to active dz in 2 yrs

- most active tb is from latent reactivation buy and also be from infc by second strain of tb- esp if immune compromised or heavy exposure to new bacilli

- classic sxs- fvr, sweats, anorexia, wt loss, weakness

- organ specific sxs- pulm- cough, CP, hemoptysis

primary tb cxr shows infc in mid to lower lungs with lymphadenopathy- reactivation is upper lobe cavitations

- signs and sxs more vaied if hiv

- lung most common site, but also lymph nodes, pleura, bone, joints. also gu, cns, abd, pericardium

Treatment

- reportable in all states- even if tx'd in private sector, reporting helps with compliance, tracking contacts, emerging resis patterns, education, outbreaks

Anti TB Drugs

- 5 first line drugs

- second line drugs are less effective or more toxic- only use if pt cannot tolerate first line or resis

Adverse Effects

INH- hepatitis, neuropathy, cns effects, elevated dilantin lvl, antabuse interaction, give with vit B6

Rif- fvr, low platelets, reduces blood levels of other drugs, caused orange urine

PZA- hyperuricemia

Ethambutol- color discrimination, visual acuity, optic neuritis

Strep- auditory and renal dysfnctn

Current Recs

- always use INH for duration of tx- effective, low cost, tolerable- if not mixed with rifampin- go 18 mo

- if double with INH/ rif- 9 mo for cure

- if triple with inh/ rif/ pza (pza for first 2 mo) shorten lenght to 6 mo

- try 3-4 meds initially and then 2 drugs afterwards

- consider local patterns of resis and schedule of administration likely to ensure adherance

- direct observation helps ensure compliance

- most common regimen- ihn/rif/pza for 8 wks, inh/rif for 16 wks with freq direct observation, and add ethambutol or streptomycin until susceptibility documented

- if cx ned, stop p 2 mo of inh/rif

- noncompliance not related to race, gender, education....cdc rec direct observation, and rewards

- get cxs- helps with resis

- baseline lfts, creatinine,cbc

- if use pza- check uric acid

- if use ethambutol- check vision and red/green color perception

- baseline cxr

- if cx neg, go by sxs and cxr at 3 mo

- sputum cx going from pos to neg - objective tx success- should change in 2 mo

- if longer than 3 mo, consider nonadherence, malabsorption, resis

- can also test urine for color in rif, urate in pza

- cx sputum at end of tx to document cure

HIV Pts

- hiv pt who adhere to standard tx do not have increased tx failure

- tx 6 mo- longer if slow response

- protease inhibitors and NNRT inhibitors mixed with rif cause rif toxicity and low levels of PI and NNRTI- avoid by using rifabutin

- do not use PI ritonivir or NNRTI delavirdine with rifabutin

Extrapulm TB

- since fewer bacilli in extrapulm site and good tissue penetration of drugs, tx should be no more difficult

- use regular 6 mo regimen

- 12 mo for meningitis in kids, bone/ joint or miliary tb

Drug Resis

- inh resis tx with rif, pza, ethambutol for 6 mo

- rif resis- inh, ethm for 18 mo or inh, pza, strep for 9 mo

- mulitidrug resis- resis to inh and rif- curable even in poor countries

Management of Latent TB

- test for tb only in high risk pt and those who will benefit from tx.

- if test low risk population- will get too many false postives

- test hiv pt, immigrants, homeless, long term care residents, health workers

- those at risk for progression from latent to active dz are immune suppressed ore recently exposed to infectious tb- highest rate of progression is from pt with both hiv and tb- also dm, crf, CA, organ xplant, ivda,

- silicosis, abnormal cxr, too thin person also indication for testing

TB Skin Test

- PPD is gold standard for latent tb testing- intradermal not multipronged

- measure induration not redness 48- 72 hrs

- 5 mm- positve if pt with weak immune response- hiv, steroid use, recent exposure and body hasn't had time to mount immune response, abnormal cxr

- 15 mm- positive if low risk pt

- 10 mm- all other pts

- if long standing infc, may actually have neg test initially- if give second skin test will be positve since first test reinvigorated immune sys- so if pt needs serial testing- do second test in 2 wks- called 2 Step Testing- if second postive represents long standing infc not recent infection

- ppd will not cause 10 mm induration in uninfected pt ever

BCG

- not recommended in US but used elsewhere

- size and persistence of tb reaction p bcg vary with bcg dose and manufacturer

- CDC rec ignoring hx of bcg when giving and interpreting ppd test since bcg only givien in high risk populations in first place

- anergy testing not recommended in tb testing of hiv pt since results highly variable and not reproducible.

Latent Tx/ PPD + Tx

- 9 mo inh if no hiv and neg cxr. 12 mo better but less compliance and more cost

- 9 mo ihn if hiv + or pos cxr or age <18yr

- can also do 2 mo of rif and pza or 4 mo of rif alone

- baseline labs if hiv +, preg, etoh, liver dz

- if duration of tx interrupted, add on additional 3 mo of inh. If lapse is greater than 3 mo, restart whole tx

- if previously tx pt reexposed to tb, repeat tx not recommended