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Introduction: Accurate clinical laboratory reference values derived from a local or regional population base are required to correctly interpret laboratory results. In Botswana, most reference intervals used to date are not standardized across clinical laboratories and are based on values derived from populations in the United States or Western Europe. Methods: We measured 14 hematologic and biochemical parameters of healthy young adults screened for participation in the Botswana HIV Pre-exposure Prophylaxis Study using tenofovir disoproxil fumarate and emtricitabine (TDF/FTC) (TDF2 Study). Reference intervals were calculated using standard methods, stratified by gender, and compared with the site-derived reference values used for the TDF2 study (BOTUSA ranges), the Division of AIDS (DAIDS) Grading Table for Adverse Events, the Botswana public health laboratories, and other regional references. Results: Out of 2533 screened participants, 1786 met eligibility criteria for participation in study and were included in the analysis. Our reference values were comparable to those of the Botswana public health system except for amylase, blood urea nitrogen (BUN), phosphate, total and direct bilirubin. Compared to our reference values, BOTUSA reference ranges would have classified participants as out of range for some analytes, with amylase (50.8%) and creatinine (32.0%) producing the highest out of range values. Applying the DAIDS toxicity grading system to the values would have resulted in 45 and 18 participants as having severe or life threatening values for amylase and hemoglobin, respectively. Conclusion: Our reference values illustrate the differences in hematological and biochemical analyte ranges between African and Western populations. Thus, the use of western-derived reference laboratory values to screen a group of Batswana adults resulted in many healthy people being classified as having out-of-range blood analytes. The need to establish accurate local or regional reference values is apparent and we hope our results can be used to that end in Botswana. [ABSTRACT FROM AUTHOR]

Background: Preexposure prophylaxis with antiretroviral agents has been shown to reduce the transmission of human immunodeficiency virus (HIV) among men who have sex with men; however, the efficacy among heterosexuals is uncertain. Methods: We randomly assigned HIV-seronegative men and women to receive either tenofovir disoproxil fumarate and emtricitabine (TDF-FTC) or matching placebo once daily. Monthly study visits were scheduled, and participants received a comprehensive package of prevention services, including HIV testing, counseling on adherence to medication, management of sexually transmitted infections, monitoring for adverse events, and individualized counseling on risk reduction; bone mineral density testing was performed semiannually in a subgroup of participants. Results: A total of 1219 men and women underwent randomization (45.7% women) and were followed for 1563 person-years (median, 1.1 years; maximum, 3.7 years). Because of low retention and logistic limitations, we concluded the study early and followed enrolled participants through an orderly study closure rather than expanding enrollment. The TDF-FTC group had higher rates of nausea (18.5% vs. 7.1%, P<0.001), vomiting (11.3% vs. 7.1%, P=0.008), and dizziness (15.1% vs. 11.0%, P=0.03) than the placebo group, but the rates of serious adverse events were similar (P=0.90). Participants who received TDF-FTC, as compared with those who received placebo, had a significant decline in bone mineral density. K65R, M184V, and A62V resistance mutations developed in 1 participant in the TDF-FTC group who had had an unrecognized acute HIV infection at enrollment. In a modified intention-to-treat analysis that included the 33 participants who became infected during the study (9 in the TDF-FTC group and 24 in the placebo group; 1.2 and 3.1 infections per 100 person-years, respectively), the efficacy of TDF-FTC was 62.2% (95% confidence interval, 21.5 to 83.4; P=0.03). Conclusions: Daily TDF-FTC prophylaxis prevented HIV infection in sexually active heterosexual adults. The long-term safety of daily TDF-FTC prophylaxis, including the effect on bone mineral density, remains unknown. (Funded by the Centers for Disease Control and Prevention and the National Institutes of Health; TDF2 ClinicalTrials.gov number, NCT00448669.) [ABSTRACT FROM AUTHOR]

Several letters to the editor, as well as the authors' response to the letters to the editor about their article "Antiretroviral Preexposure Prophylaxis for Heterosexual HIV Transmission in Botswana" in the August 2, 2012 issue are presented.

This study examined study product adherence and its determinants in the Botswana oral pre-exposure prophylaxis efficacy trial. Among the 1,219 participants, the mean adherence by pill count and 3-day self-report was 94 % for each. In multivariable models, pill count adherence was significantly associated with adverse events (nausea, dizziness, vomiting) (RR 0.98 95 % CI 0.98-1.00; p = 0.03) and side effect concerns (RR 0.98 95 % CI 0.96-0.99; p = 0.01). Self-reported adherence was significantly associated with having an HIV-positive partner (RR 1.02 95 % CI 1.00-1.04; p = 0.02) and Francistown residence (RR 0.98 95 % CI 0.96, 0.99; p = 0.0001). Detectable drug concentrations showed modest associations with self-report and pill count adherence, and drug levels were higher among those self-reporting 100 % adherence than those reporting <100 %. Most common adherence barriers involved refill delays and other logistic challenges; cellphone alarm reminder use was the most common facilitator.

Objective: Thirty-six months of isoniazid preventive therapy (36IPT) was superior to 6 months of IPT (6IPT) in preventing tuberculosis (TB) among HIV-infected adults in Botswana. We assessed the posttrial durability of this benefit., Design: A 36-month double-blind placebo controlled trial (1 : 1 randomization) with recruitment between November 2004 and July 2006 and observation until June 2011., Methods: One thousand, nine hundred and ninety-five participants were followed in eight public health clinics. Twenty-four percent had a tuberculin skin test ≥5 mm (TST-positive). A minimum CD4 lymphocyte count was not required for enrolment. Antiretroviral therapy (ART) was provided in accordance with Botswana guidelines; 72% of participants retained by June 2011 had initiated ART. Multivariable analysis using Cox regression analysis included treatment arm, TST status, ART as a time-dependent variable and CD4 cell count at baseline and updated at 36 months., Results: In the posttrial period, 2.13 and 2.14 per 100 person-years accumulated, whereas 0.93 and 1.13% TB incidence rates were observed in the 36IPT and 6IPT arms, respectively (P = 0.52). The crude hazard ratio of TB during the trial and posttrial was 0.57 [95% confidence intervals (CI) 0.33, 0.99] and 0.82 (95% CI 0.46, 1.49), and when restricted to TST-positive participants was 0.26 (95% CI 0.08, 0.80) and 0.40 (95% CI 0.15, 1.08), respectively. Multivariable analysis showed that ART use was associated with reduced death (adjusted hazard ratio 0.36, 95% CI 0.17-0.75) but not TB (0.92, 95% CI 0.55-1.53) in the posttrial period., Conclusion: The benefit of 36IPT for TB prevention declined posttrial in this cohort. Adjunctive measures are warranted to prevent TB among HIV-infected persons receiving long-term ART in TB-endemic settings., Competing Interests: The authors have no conflicts of interest to declare.

We examined CD4 cell count and plasma viral load patterns among Botswana TDF/FTC Oral HIV Prophylaxis Trial (TDF2 study) participants who seroconverted, comparing participants assigned to receive tenofovir/emtricitabine with participants assigned to receive placebo. We also evaluated for antiretroviral drug resistance among the breakthrough HIV infections. Among nine seroconverters assigned to tenofovir/emtricitabine and 24 to placebo, there were no significant differences in their CD4 cell count or viral load profiles over time. Of the four participants who seroconverted on-study while receiving tenofovir/emtricitabine, none became infected as a result of drug-resistant HIV; moreover, no resistance mutations emerged following seroconversion.