Pooled nucleic acid testing to detect antiretroviral treatment failure in Mexico.
BACKGROUND
Similar to other resource-limited settings, cost restricts availability of viral load monitoring for most patients receiving antiretroviral therapy in Tijuana, Mexico. We evaluated if a pooling method could improve efficiency and reduce costs while maintaining accuracy.


METHODS
We evaluated 700 patient blood plasma specimens at a reference laboratory in Tijuana for detectable viremia, individually and in 10 × 10 matrix pools. Thresholds for virologic failure were set at ≥500, ≥1000 and ≥1500 HIV RNA copies per milliliter. Detectable pools were deconvoluted using pre-set algorithms. Accuracy and efficiency of the pooling method were compared with individual testing. Quality assurance (QA) measures were evaluated after 1 matrix demonstrated low efficiency relative to individual testing.


RESULTS
Twenty-two percent of the cohort had detectable HIV RNA (≥50 copies/mL). Pooling methods saved approximately one third of viral load assays over individual testing, while maintaining negative predictive values of >90% to detect samples with virologic failure (≥50 copies/mL). One matrix with low relative efficiency would have been detected earlier using the developed QA measures, but its exclusion would have only increased relative efficiency from 39% to 42%. These methods would have saved between $13,223 and $14,308 for monitoring this cohort.


CONCLUSIONS
Despite limited clinical data, high prevalence of detectable viral loads and a contaminated matrix, pooling greatly improved efficiency of virologic monitoring while maintaining accuracy. By improving cost-effectiveness, these methods could provide sustainability of virologic monitoring in resource-limited settings, and incorporation of developed QA measures will most likely maximize pooling efficiency in future uses.
Department of Medicine, University of California, San Diego, La Jolla, CA 92093-0711, USA. mtilghman@ucsd.edu
Myres W
MW
Tilghman
Don Diego
DD
Guerena
Alexei
A
Licea
Josué
J
Pérez-Santiago
Douglas D
DD
Richman
Susanne
S
May
Davey M
DM
Smith
D016903:Drug Monitoring / Q000191:economics / Q000379:methods*; D006678:HIV / Q000235:genetics* / Q000302:isolation & purification*; D015658:HIV Infections / Q000188:drug therapy* / Q000821:virology*; D006801:Humans; D008800:Mexico; D010949:Plasma / Q000821:virology; D012367:RNA, Viral / Q000097:blood; D013048:Specimen Handling / Q000191:economics / Q000379:methods*; D017211:Treatment Failure; D019562:Viral Load / Q000191:economics / Q000379:methods*
D012367:RNA, Viral