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Toward “real time” HIV/STI diagnosis in the HIV/AIDS Program of Mexico City

Improvement Report
L. Juárez-Figueroa (corresponding author), P. Iracheta, A. González-Rodriguez.

Topics: HIV laboratory services

Region and Country: Mexico

Organization: HIV/AIDS Program of Mexico City
The Report


The HIV Program of Mexico City  (HIVPMC ) gives Voluntary Counseling and Testing  (VCT) with rapid tests to MSM, SW, TTT and other groups like female partners of HIV+ men and offers HIV confirmation for PMTCT and other City programs.
HIVPMC currently provides also laboratory support to a program for HIV/STI diagnosis and treatment among inmates of Mexico City prisons.
Until recently HIVPMC lacked of opportune HIV confirmation and other STI serological diagnosis mainly due to slow and costly referral to a centralized system that delayed laboratory results feedback from several weeks to several months.
This prevented opportune medical decisions, and provoked loss of adherence among VCT clients.
In order to speed up HIV/STI diagnosis, to reduce costs and in general to improve the quality of data output while procuring at the same time a suitable laboratory platform for HIV/STI population surveys, we instrumented an automated system already used across the world for blood donors screening and replaced traditional WB confirmation with a quicker strip test.
The experience of the first 5 months applying this approach with VCT clients is presented.


The group studied herein consisted of 2,137 male and 1,270 female consecutive clients who requested VCT at Condesa Clinic between December 2009 and April 2010.
A venous blood sample was obtained from all clients with an HIV+ rapid test result at VCT for HIV confirmation and other STI serology tests.
We instrumented Abbott Architect HIV 1&2 Ag/Ab Combo, Anti- HBc, Anti-HCV and Syphilis TP quimioluminiscence immunoassay running in Architect i2000 equipment.
HIV+ samples were confirmed with Orgenics HIV 1&2 CombFirm II.
Anti-HBc+ were tested with Determine HBsAg to asses HBV carrier status.
Syphilis TP+ were assayed with tittered V.D.R.L.
Additionally, to asses if there exist possible incident cases lost by rapid HIV antibody tests, a subgroup of 660 consecutive VCT clients no reactive to HIV rapid test from March 2010, 421 male and 239 female were further assayed in sera pools with Abbott Architect HIV Ag/Ab and in plasma pools with NAAT, Roche Ampliscreen Cobas HIV.


Among 2137 men, 398 (18.6%) were confirmed as HIV positive.
HIV rapid test detected 396 samples further confirmed as positive with Abbott Architect HIV 1&2 Ag/Ab Combo and Orgenics HIV 1&2 CombFirm II.
Among a subgroup of 421 consecutive men samples which tested non reactive with the rapid test, 2 samples were reactive with Abbott Architect HIV 1&2 Ag/Ab Combo and NAAT Roche Ampliscreen Cobas HIV but negative with Orgenics HIV 1&2 CombFirm II, thus were considered incident cases with detectable p24 Ag and HIV RNA but not detectable HIV antibody.
HIV rate in men and other STI co-infection rates are shown in Table 1.
Among 1270 women, 26 (2.1%) were reactive with the rapid test and confirmed as HIV positive with Abbott an Orgenics tests. No additional positive samples were found with Ag/Ab test and NAAT in 239 consecutive rapid test negative selected samples.
HIV rate in women and other STI co-infection rates are shown in Table 2.
Laboratory results were delivered to counselors in less than 48 hours, with the exception of NAAT results which were delivered in two weeks.


Table 1. VCT, HIV/STI coinfections. Men, Dic. 2009-April 2010.


Table 2. VCT, HIV/STI coinfections. Women. Dic. 2009-April 2010.     




The group of male clients requesting VCT at our clinic shows one of the highest HIV prevalence found among different population groups in Mexico.
The rate of co-infections with HBV an T. Pallidum in this group is high, thus the fast assessment of HIV/STI while increases adherence also allows on time treatment and control of co-infections.
The use of a 4th. generation HIV Ag/Ab test that significantly reduces the detection “window period” proved more appropriate for HIV detection in this high prevalence group allowing the recognition of HIV infections before HIV antibody are detectable.
Four generation HIV rapid test are at present not available in Mexico, hence to be able of earlier infections detection among VCT men clients we now routinely test samples from all non reactive individuals with a 4th. Generation HIV Ag/Ab immunoassay.
The women of this group showed a lower HIV+ rate and mostly associated with HIV+ partners. Rapid HIV tests detecting only HIV antibody seems adequate in terms of sensitivity in this group.