Are survey-based estimates of the burden of drug resistant TB too low? Insight from a simulation study.
BACKGROUND
The emergence of tuberculosis resistant to multiple first- and second-line antibiotics poses challenges to a global control strategy that relies on standard drug treatment regimens. Highly drug-resistant strains of Mycobacterium tuberculosis have been implicated in outbreaks and have been found throughout the world; a comprehensive understanding the magnitude of this threat requires an accurate assessment of the worldwide burden of resistance. Unfortunately, in many settings where resistance is emerging, laboratory capacity is limited and estimates of the burden of resistance are obtained by performing drug sensitivity testing on a sample of incident cases rather than through the use of routine surveillance.


RESULTS
Using an individual-based dynamic tuberculosis model to simulate surveillance strategies for drug resistance, we found that current surveys may underestimate the total burden of resistant tuberculosis because cases of acquired resistance are undercounted and resistance among prevalent cases is not assessed. We explored how this bias is affected by the maturity of the epidemic and by the introduction of interventions that target the emergence and spread of resistant tuberculosis.


CONCLUSIONS
Estimates of drug resistant tuberculosis based on samples of incident cases should be viewed as a lower bound of the total burden of resistance.
Division of Social Medicine and Health Inequalities, Brigham and Women's Hospital, Boston, Massachusetts, United States of America. tcohen@hsph.harvard.edu
Ted
T
Cohen
Caroline
C
Colijn
Bryson
B
Finklea
Abigail
A
Wright
Matteo
M
Zignol
Alexander
A
Pym
Megan
M
Murray
D003625:Data Collection; D004196:Disease Outbreaks; D006801:Humans; D015994:Incidence; D011159:Population Surveillance; D015995:Prevalence; D018088:Tuberculosis, Multidrug-Resistant / Q000188:drug therapy / Q000453:epidemiology* / Q000382:microbiology / Q000635:transmission