Volume 14, Number 5—May 2008
Scale-up of Multidrug-Resistant Tuberculosis Laboratory Services, Peru
|Programmatic and epidemiologic features||Optimal DST characteristics|
|Standardized versus individualized regimens|
|Standardized regimens for MDR based on regional resistance patterns||Centralized, complete DST (i.e., first- and second-line drugs) of representative samples to guide standardized treatment regimen; turnaround time less important|
||Rapid, point-of-care DST optimal to accommodate high demand and minimize turnaround time. Semi-individualized regimens may be constructed if only DST to first-line drugs performed.
|Who is tested for DST?|
|Narrow DST indications (e.g., treatment failures only)||High pretest probability for MDR TB; therefore, optimal to perform DST to first- and second-line drugs to guide regimen design|
|Moderate DST indications (e.g., healthcare worker, smear-positive in second month of DOTS)||Rapid DST to first-line drugs to screen MDR TB versus non–MDR TB. If individualized treatment, drug-resistant samples may be referred for complete DST. Sensitivity may be more important than specificity because of greatest illness from failing to start appropriate treatment in patients with drug resistance.|
||Rapid DST to first-line drugs to screen MDR TB versus non–MDR TB. Rapid point-of-care testing (decentralized) optimal. If individualized treatment, drug-resistant samples may be referred for complete DST. Sensitivity may be more important than specificity.
|Patients with smear-negative disease (e.g., HIV, children)||Direct DST by using liquid medium or indirect DST after culture by liquid medium. Rapid turnaround time important given high illness rates in these risk groups.|
|High rates of resistance to second-line
drugs (XDR TB)
||Complete DST if high rates of resistance to second-line drugs, including XDR. If limited resources, DST to first-line drugs plus key second-line drugs (e.g., quinolone, kanamycin) to enable identification of XDR TB cases.
|Management while awaiting DST results|
|Empiric first-line regimen||Greater risk for inadequate treatment of MDR TB cases; rapid testing more important|
|Empiric MDR TB regimen||Less risk for inadequate treatment of MDR TB cases, excess cost and toxicity for non–MDR TB cases. Complete DST results permit adjustment of empiric MDR TB therapy.|
*DST, drug susceptibility testing; MDR TB, multidrug-resistant tuberculosis; XDR TB, extensively drug-resistant TB; DOTS, directly observed treatment, short course.
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