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. Author manuscript; available in PMC: 2023 Mar 1.
Published in final edited form as: J Acquir Immune Defic Syndr. 2022 Mar 1;89(3):310–317. doi: 10.1097/QAI.0000000000002859

Tenofovir Diphosphate in Dried Blood Spots in pregnant and postpartum women with HIV in Kenya: a novel approach to measuring peripartum adherence.

Lisa L Abuogi 1, Jose Castillo-Mancilla 2, Karen Hampanda 3, Kevin Owuor 6, Tobias Odwar 4, Maricianah Onono 4, Anna Helova 5, Janet M Turan 5, Peter L Anderson 6
PMCID: PMC8837670  NIHMSID: NIHMS1753746  PMID: 34889866

Abstract

Background:

Adherence to antiretroviral therapy (ART) among pregnant and postpartum women with HIV (PWLWH) is critical to promote maternal health and prevent HIV transmission. Tenofovir diphosphate (TFV-DP) in dried blood spots (DBS) is an objective assessment of cumulative ART adherence that has not been fully assessed in PWLWH.

Setting:

southwestern Kenya

Methods:

PWLWH receiving tenofovir disoproxil fumarate-based ART from 24 health facilities provided DBS samples at three time points (pregnancy/early postpartum [PP], 6 months PP, and 9–12 months PP). Thresholds for daily adherence were defined as TFV-DP in DBS ≥650 fmol/punch in pregnancy and ≥950 postpartum. Descriptive analysis is presented. Cluster adjusted Chi squares and t-tests were used to test for association with clinical and demographic factors.

Results:

A total of 419 DBS samples were collected from 150 PWLWH. Median TFV-DP in DBS was lowest, 552 fmol/punch (Interquartile range (IQR 395,759) in pregnancy and declined over time postpartum: 914 (IQR 644,1176) fmol/punch early PP, 838 (IQR 613,1063) fmol/punch 6 months PP, and 785 (IQR 510,1009) fmol/punch 9–12 months, p<0.001. Only 42% of samples in pregnancy and 38.5% of samples in PP met thresholds for daily adherence. Clinical or demographic factors were not associated with suboptimal adherence levels.

Conclusion:

Cumulative ART exposure (i.e., adherence) in PWLWH, quantified by TFV-DP in DBS, demonstrated a stepwise decrease postpartum. Most women demonstrated less than daily adherence throughout the peripartum period. Use of TFV-DP in DBS as a measure of cumulative ART adherence could help optimize health outcomes in PWLWH and their infants.

Keywords: adherence, women living with HIV, prevention of mother to child transmission

Introduction

Despite the remarkable scale up of antiretroviral therapy (ART) among pregnant women living with HIV globally, perinatal transmission of HIV is the main cause of the 160,000 new pediatric infections annually.1–3 As obstacles to ART access are being addressed, attention is increasingly focused on adherence to treatment. ART improves maternal health outcomes and reduces the risk of perinatal transmission of HIV,4 but its long-term benefits are largely dependent on continuously high adherence.5,6 A substantial number of pregnant and postpartum women continue to face challenges with optimal ART adherence, leading to increased risks of perinatal and sexual transmission and adverse maternal health and survival.6–8

While adherence to ART is essential, quantifying long term ART adherence is notoriously difficult. HIV viral load is a common surrogate for ART adherence. Unfortunately, HIV viral load is not obtained with sufficient frequency through the standard of care in most high HIV prevalence low- and middle-income countries (LMIC) to impact clinical management in the critical peripartum period where perinatal transmission occurs.9,10 Further, an undetectable viral load is not equivalent to complete adherence as new, more potent, ART regimens can achieve and sustain viral suppression without perfect adherence.11–13 Moreover because current ART regimens are more forgiving of missed doses, infrequent viral load testing may not accurately reflect overall adherence.11,13 Therefore, objective and reliable tools for measuring cumulative ART adherence over time at critical points in the peripartum period are needed to improve clinical case management of peripartum WLHIV (PWLWH).14

The quantification of tenofovir diphosphate (TFV-DP) concentrations in red blood cells using dried blood spots (DBS) is an objective assessment of cumulative (i.e., long-term) drug adherence and drug exposure that is associated with viral suppression,15 predictive of future viremia,16,17 and reflective of improvements in adherence following behavioral interventions.18 The long half-life of TFV-DP (17 days) in red blood cells has been translated into an adherence gradient used to estimate average TFV-DP dosing, which allows for estimation of cumulative adherence and exposure over the preceding 6–8 weeks in people using tenofovir as part of ART or pre-exposure prophylaxis (PrEP) similar to the use of hemoglobin A1c (HbA1c) in patients living with diabetes.19,20 TFV-DP concentrations in DBS have been shown to correlate with decreased adherence to ART as measured by pharmacy refill in women with HIV in the United States.21 However, despite its potential utility, cumulative adherence measured by TFV-DP concentrations in DBS has not been adequately studied in PWLWH.

Pregnancy and the early peripartum period are characterized by rapid physiologic changes which impact tenofovir drug levels in blood which necessitates careful interpretation of drug concentrations relative to the time period they are measured.22,23 Recent work in HIV-uninfected African adolescent girls and young women on tenofovir-based PrEP under directly observed dosing demonstrated significantly lower TFV-DP concentrations in pregnancy compared to postpartum and provided proposed thresholds correlated to number of doses taken per week.24,25 Tenofovir disoproxil fumarate (TDF) is part of the first-line regimen for PWLWH in Kenya,26 providing the opportunity to objectively quantify ART adherence using this sensitive pharmacological assessment.

To better understand longitudinal adherence patterns in PWLWH and to explore the use of TFV-DP DBS measurement in this population, we report on TFV-DP concentrations in DBS in serial samples collected from a sub-sample of PWLWH participants enrolled in a trial in southwestern Kenya.

Methods

This was a nested longitudinal cohort study. During 2015–2019, we conducted a cluster randomized, 2×2 factorial, controlled trial to evaluate the individual and combined effect of text messaging and community mentor mother home visits on maternal postpartum retention in care and ART adherence in southwestern Kenya (MOTIVATE).27 A total of 1331 pregnant women with HIV were enrolled in the study and followed to 12 months postpartum. A sub-sample of 150 participants from this trial underwent serial DBS collection during pregnancy and postpartum between January 2018 and March 2019. (Figure 1) We hypothesized that concentrations of TFV-DP would decrease postpartum and that factors associated with lower TFV-DP concentrations would include younger age, primigravida, and new HIV diagnosis in pregnancy.

Figures 1.

Figures 1.

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Flow diagram of MOTIVATE study participants enrolled in tenofovir drug level sub-study

Setting:

Study sites included 24 government health facilities in southwestern Kenya- a region with the highest HIV prevalence in the country. ART treatment was available at no cost to all pregnant and postpartum women. Routine viral load monitoring was not introduced until mid-way through study enrollment and follow up. While Kenyan guidelines recommended viral load testing six months after ART initiation and every six months throughout breastfeeding, uptake of this recommendation was low while viral load testing was scaled up. HIV testing for HIV exposed infants per Kenyan guidelines included HIV DNA PCR testing at six weeks, six and 12 months of age and antibody testing at 18 months.

Participants:

The Mother and Infant Visit Adherence and Treatment Engagement (MOTIVATE) study enrolled PWLWH identified in the antenatal clinics who were 18 years or older, had access to a mobile phone, and were willing to have home visits to receive the MOTIVATE study interventions (text messaging and community mentor mother home visits). We recruited 150 MOTIVATE study participants receiving TDF-based ART regimens for a minimum of 10 weeks for this sub-study (to achieve TFV-DP steady-state at time of first DBS collection). A purposively selected subsample of MOTIVATE participants were recruited (Figure 1) to collect DBS for TFV-DP testing based on pregnancy status, with preference for currently pregnant or less than three months postpartum at time of first DBS collection. Women who met eligibility criteria were recruited until the target sample of 150 participants was achieved.

Laboratory procedures:

DBS samples were collected by trained study nurses at three time points for each participant: pregnancy or within three months postpartum, at six months and nine to 12 months postpartum at participating health facilities from January 2018 to May 2019. Participants had the first sample collected either during pregnancy or 0–3 months postpartum with preference for collection during pregnancy if possible. Samples were prepared by spotting 25 μL of whole blood obtained from venipuncture onto Whatman 903 filter paper, as described elsewhere.21 DBS cards were dried overnight and subsequently packaged with desiccant packets and humidity indicator, then stored at −80° Celsius. Samples were then shipped to the Colorado Antiviral Pharmacology Laboratory where TFV-DP testing was performed.

Quantification of intracellular TFV-DP in DBS was conducted using validated methods.28,29 In brief, first a micropuncher was used to remove a three millimeter-diameter disc from the DBS card. Then each disc was extracted with 500 µL of 70:30 methanol-H2O with sonication and centrifugation and stored at −80 ºCelsius until analysis. Next, supernatants derived from this process were analyzed using liquid chromatography–tandem mass spectrometry assays (LC-MS/MS).28 Plasma concentrations of TFV were measured using a validated LC-MS/MS method, as previously described.30

Data collection and outcome measures:

Demographic and clinical data were abstracted by trained data clerks as part of the MOTIVATE study from routine medical records including the Kenyan Ministry of Health HIV clinic visit forms and clinic registers and entered into laptops using the Open Data Kit (ODK) platform. ART adherence was also measured via self-report and classified as per Kenya guidelines as good (>95% of pills taken since last clinic visit), fair (85%−94%), or poor (<85%). TFV-DP concentration thresholds were derived from recent research in African women and adolescents on PrEP during pregnancy and post-partum as described in Table 1. For DBS samples with values below the lower limit of quantification (LLOQ) a value of 12.5fmol/punch (the midpoint between zero and the assay LLOQ (25 fmol/sample) was assigned, and those samples were included in the analysis. This affected a total of five samples from three participants: two participants had one sample each and one participant had three samples all below LLOQ.

Table 1.

Defined thresholds for tenofovir diphosphate concentrations and adherence interpretations in pregnant and postpartum women.31

Adherence Interpretation Pregnant women (fmol/punch) Post-partum women (fmol/punch)
~ 7 doses per week ≥ 650 ≥ 950
2–6 doses per week 200–649 250–949
<2 doses per week <200 <250
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Analysis

Samples were categorized and analyzed based on timing of collection into four categories (pregnancy, 0–3, 6, or 9–12 months postpartum) based on the different adherence thresholds for pregnant and postpartum women. Descriptive analysis was done using counts (proportions) and medians (interquartile range [IQR]). Cluster adjusted chi squares and t-tests were used to test for associations with clinical and demographic factors. Box plots were used to display the data. The extended Cochran Mantel-Haenszel Stratified test was used to perform repeated measures nonparametric test (Friedman test) on differences of TFV-DP concentrations at pregnancy, 0–3, 6 and 9–12 months. Box graphs were used to display TFV-DP concentrations by period and intervention. All tests were evaluated for significance at the 5% level. All analyses were performed using Stata 15.1 (StataCorp. 2017. Stata Statistical Software: Release 15. College Station, TX: StataCorp LLC.).

Results

A total of 419 DBS samples were collected from 150 women. The median age of participants was 28 years (interquartile range (IQR) 25 to 32) with a mean of 3.4 pregnancies. Only 10 (7%) were primigravida and the majority (n=127,88.8%) already knew their HIV diagnosis prior to this pregnancy. Median time on ART at time of first DBS sample collection was 38 months (IQR 17–54). Retention in this subsample was high with 128 (85%) participants providing three DBS samples; 13 (8.7%) participants only two samples; and 6 (4%) only one sample.

Overall, 17 women had samples obtained during pregnancy, all in the third trimester, with a median TFV-DP concentration in DBS of 552 fmol/punch (IQR 395,759). Median TFV-DP concentrations at the early, mid- and late-postpartum periods were 914 (644,1176), 838 (613,1063), and 785 (510,1009) fmol/punch, respectively. (Figure 2) Using a cut-off of ≥650fmol/punch for optimal adherence (7 doses per week), 7 out of 17 (41.2%) pregnant women demonstrated optimal adherence. During the PP period, women achieving optimal adherence benchmark defined as ≥950 fmol/punch were 64 (47.8%) early PP (0–3 months) 54 (37.0%) at six months PP, and 41 (31.6%) late postpartum PP (p<0.001). (Table 2) Between 2–6 percent of women demonstrated TFV-DP concentrations in DBS equivalent to less than two TDF doses per week in each time period.

Figure 2.

Figure 2.

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Median tenofovir-diphosphate (TFV-DP) concentrations (fmol/punch) during pregnancy, early-, mid- and late-postpartum in Kenya (Interquartile range (IQR), and 95% CI)

Table 2.

Tenofovir Diphosphate levels in pregnant and postpartum women on ART by adherence threshold.

Adherence Interpretation Thresholds Pregnant women Pregnant women
N=17
N(%)		 Thresholds Post-partum women 0–3 months postpartum
N=134
N(%)		 6 months postpartum N=143 N(%) 9–12 months postpartum N=131
N(%)
~ 7 doses per week ≥650 7(41) ≥950 64(48) 54(38) 41(31)
2–6 doses per week 200–649 9(53) 250–949 68(51) 82(57) 84(64)
<2 doses per week <200 1(6) <250 2(2) 7(5) 6(5)
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We did not identify any association between clinical and demographic variables and TFV-DP concentrations in DBS during pregnancy (data not shown) or in postpartum women, except those women with lower TFV-DP concentrations were more likely to be on a non-standard TDF-containing regimen (Pregnancy; p=0.04, 0–3 months PP; p=0.009). (Table 3). Most women on non-standard regimens (>85%) were on TDF plus lamivudine and nevirapine and the remainder were on second line ART including TDF and lopinavir/ritonavir. Median TFV-DP concentrations in DBS over time by arm of the parent trial did not differ significantly in the control arm as compared to the intervention arms (data not shown).

Table 3.

Comparison of characteristics of postpartum women living with HIV with suboptimal versus optimal adherence quantified using tenofovir diphosphate in dried blood spots.

Total TFV-DP DBS <950 (fmol/punch) n=70 TFV-DP DBS ≥950 (fmol/punch) n=64 p-value Total TFV-DP DBS <950 (fmol/punch) n=88 TFV-DP DBS ≥ 950 (fmol/punch) n=54 p-value Total TFV-DP DBS <950 (fmol/punch) n=89 TFV-DP DBS ≥950 (fmol/punch) n=41 p-value
0–3 months postpartum 6 months postpartum 9–12 months postpartum
Median Age (years) 28(25–32) 30(26–32) 28(25–32) 0.247 28(25–32) 28(25–32) 28(25–33) 0.923 28(25–32) 28(25–33) 28(25–32) 0.996
 
Hemoglobin median(IQR) 11(10–12) 12(9–12) 11(10–12) 0.691 11(10–12) 12(11–12) 11(10–11) 0.623 11(10–12) 11(10–12) 11(10–12) 0.888
 
Body Mass Index 0.247 0.9001 0.0578
Underweight (<18.50) 10(7.9) 8(12.1) 2(3.3) 8(6.0) 4(4.8) 4(8.0) 8(6.5) 2(2.4) 6(15)
Normal (18.50–24.99) 91(71.7) 44(66.7) 47(77) 96(71.6) 60(71.4) 36(72) 89(71.8) 63(75) 26(65)
Overweight (25.00–29.99) 21(16.5) 12(18.2) 9(14.8) 21(15.7) 13(15.5) 8(16) 18(14.5) 12(14.3) 6(15)
Obese (≥30) 5(3.9) 2(3) 3(4.9) 9(6.7) 7(8.3) 2 (4) 9(7.3) 7(8.3) 2(5)
 
Gravida 0.84 0.912 0.4056
≤ 1 9(6.9) 5(7.4) 4(6.5) 10(7.3) 6(7.0) 4(7.8) 10(7.9) 8(9.3) 2(5)
≥2 121(93.1) 63(92.6) 58(93.5) 127(92.7) 80(93) 47(92.2) 116(92.1) 78(90.7) 38(95)
 
HIV status at time of pregnancy 0.464 0.8456 0.3791
Known Positive 114(87.7) 61(89.7) 53(85.5) 122(89.1) 76(88.4) 46(90.2) 112(88.9) 75(87.2) 37(92.5)
Positive 16(12.3) 7(10.3) 9(14.5) 15(10.9) 10(11.6) 5(9.8) 14(11.1) 11(12.8) 3(7.5)
 
ART Regimen 0.009 0.1431 0.2864
TDF-3TC-EFV 100(76.9) 46(67.6) 54(87.1) 105(76.6) 60(69.8) 45(88.2) 100(79.4) 66(76.7) 34(85)
TDF + Other 30(23.1) 22(32.4) 8(12.9) 32(23.4) 26(30.2) 6(110.8) 26(20.6) 20(23.3) 6(15)
 
Time on ART at initial sample collection (months)
Median (IQR) 39(18–54) 40(19–57) 34(18–48) 0.446 39(18–56) 40(17–57) 32(18–54) 0.815 36(17–53) 38(17–53) 34(19–62) 0.57
 
Self-reported adherence closest to sample collection 0.338 0.440 0.494
Poor 1(0.8) 1(1.5) 0 1(0.7) 0(0) 1(2) 0 0 0
Good 129(99.2) 67(98.5) 62(100) 136(99.3) 86(100) 50(98) 0.5175 126(100) 86(100) 40(100)
 
History of viremia in pregnancy or postpartum 0.867 0.300 0.4327
Yes 64(49.2) 33(48.5) 31(50) 67(48.9) 36 (41.9) 31(60.8) 60(47.6) 43(50) 17(42.5)
No 66(50.8) 35(51.5) 31(50) 70(51.1) 50(58.1) 20(39.2) 66(52.4) 43(50) 23(57.5)
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Among the 150 women included, all live born infants (n=151) underwent at least one HIV test per Kenya guidelines. One infant was identified as HIV positive at 6 weeks of age with HIV DNA polymerase chain reaction testing and was born to a participant in the community mentor mother intervention arm who had two TFV-DP DBS samples, one at 8 weeks PP and one at 6 months PP, with TFV-DP concentration below the level of quantification (undetectable) and DBS at 11 months PP with 841 fmol/punch. Viral load testing available for this mother showed 89 copies/ml during the third trimester of pregnancy and 372 copies/ml around 4 months PP, both below the level of 1000 copies/ml which triggers further intervention per Kenyan guidelines.

Discussion:

This study of pregnant and postpartum women living with HIV on TDF-based ART is the first to objectively quantify cumulative ART adherence longitudinally from pregnancy through 12 months postpartum using TFV-DP concentrations measured in DBS. We found that cumulative ART exposure was suboptimal throughout the peripartum period and declined over time in the postpartum period. Less than half of women demonstrated daily adherence in pregnancy and early postpartum and only a third did by 6–12 months postpartum using recently established thresholds for TFV-DP concentrations.31 In addition, our study objectively demonstrated decreasing TFV-DP concentrations postpartum in women followed longitudinally from pregnancy or early postpartum through 9–12 months postpartum confirming prior research suggesting decreased ART adherence postpartum.6,8,32,33 Additionally, like past research on tenofovir pharmacokinetics in African adolescents and young women without HIV, we found lower TFV-DP concentrations during late pregnancy as compared to postpartum.22

Despite the lower overall TFV-DP level in women during pregnancy, a larger proportion of women (>40%) showed levels consistent with daily adherence than any other time point captured. Yet nearly 60% still demonstrated less than daily adherence in pregnancy increasing to nearly 70% with less than daily adherence by 9–12 months postpartum. As TDF is co-formulated with lamivudine and efavirenz as a once daily fixed dose combination pill in Kenya, this implies that women were missing their entire ART regimen frequently. Non-adherence to ART in the peripartum period has been associated with higher plasma HIV viral load in pregnant women, and substantially higher plasma and breastmilk HIV RNA concentration during the breastfeeding period.34–36 The result of non-adherence may be new pediatric HIV infections and poor maternal health outcomes. While we identified a large proportion of women at all time points with suboptimal TFV-DP concentrations, only one infant transmission was found in a woman with undetectable TFV-DP indicating perfect adherence may not be necessary but identifying women with poor adherence is still important to prevent perinatal transmissions. Future work is needed to determine correlations of TFV-DP concentrations and HIV transmission to infants.

Adherence to antiretroviral treatment (ART) during the critical peripartum period is known to be suboptimal in many women globally. For example, a review of large studies in Kenya, South Africa, and Zambia found that 76% of pregnant women adhered to ART during pregnancy, but only 53% did so post-birth.33,37 While motivation for adherence during pregnancy may be high, numerous studies demonstrate decreased adherence in the postpartum period.6,8,32 Barriers identified commonly include a complex set of individual, interpersonal, and structural/societal barriers, such as low HIV/ART knowledge, stigma, lack of family or partner support, cultural traditions, staff shortages, poor staff-client interactions, and lack of service accessibility.38–41 While several studies have identified factors associated with poor adherence in PWLWH, our study did not find associations between demographic (e.g. age) or clinical factors (e.g. time on ART, history of viremia) with the TFV-DP thresholds used. We did find an association with non-standard TDF-containing regimens, predominantly women on nevirapine-based ART and a few women on second line lopinavir/ritonavir ART including TDF and lower TFV-DP concentrations. Since both nevirapine and lopinavir-based regimens require twice daily dosing and once daily dosing is associated with improved adherence, it is possible that the women on these regimens were more likely to miss doses.42,43 Further, women on second-line ART have already experienced treatment failure and may be more likely to continue to have unresolved adherence issues resulting in lower TFV-DP concentrations.44

This study also highlights the potential utility of longitudinal TFV-DP DBS monitoring of cumulative ART adherence in PWLWH in low and middle-income countries (LMICs). A variety of nonpharmacologic approaches to measuring ART adherence are in practice, but most are subjective and lead to overestimation of adherence (self-report, pill counts, recall, pharmacy refill adherence).45–47 Other measures with better correlation to adherence, such as electronic medication monitoring (e.g., WisePill and MEMS), are cost prohibitive in LMICs and subject to patient tampering.48–51 Traditional pharmacologic measures of adherence to antiretrovirals (ARVs) with short half-lives (plasma and urine drug concentrations) similarly have limitations.52–54 For example, plasma ARV concentrations and HIV viral load can be confounded by ‘‘white coat’’ adherence (improved adherence preceding clinic visits) and cannot provide information about long-term cumulative adherence due to the short half-lives of most ARVs in these matrices.55 Since, TFV-DBS concentrations reflect 6–8 weeks of prior adherence, “white coat” adherence would need to be prolonged to impact adherence interpretation.

In comparison, pharmacologic measures with long half-lives (concentrations in hair and DBS) provide objective quantification of sustained drug intake. Drug concentrations in hair have shown to be highly informative about drug exposure and cumulative adherence, but this approach is not available in clinical practice and collection of hair in certain populations, including African women, can be challenging due to cultural concerns and shaved or very short hair whereas blood collection is an accepted part of routine HIV care.56 TFV-DP in DBS has recently been introduced as an objective and quantitative assessment of long-term drug adherence and exposure to ART in people with HIV.15,21,57 In contrast to hair, DBS are obtained via venipuncture (or fingerstick) through routine blood collection already happening in the clinic, thus minimizing barriers on acceptability.

Additionally, low concentrations of TFV-DP in DBS has been shown to be predictive of future viremia (>20 copies/mL) — even in people with HIV who are virologically-suppressed at the time of the visit, providing the opportunity to identify pregnant and postpartum women at higher risk of viremia during the peripartum period.58,59 Intermediate TFV-DP concentrations are also associated with increased drug resistance mutations.60 To maximize the durability of first-line ART regimens, including dolutegravir-based regimens which are often combined with TDF in LMIC, monitoring of TFV-DP concentrations may serve as an early warning indicator for the development of drug resistance. Another application may be for peripartum women at risk for HIV receiving oral PrEP formulations. Given the higher risk of HIV acquisition during pregnancy and early postpartum combined with suboptimal adherence measurements already described, there is need for an objective, cumulative approach to measuring PrEP adherence both to improve adherence and reduce risk of HIV acquisition during this vulnerable period. Importantly, this pharmacologic measure of long-term adherence has already been implemented in South Africa and can be replicated in other LMIC settings. Similar to algorithms developed in LMIC to determine which patients should undergo resource-intensive drug resistance testing, approaches to using TFV-DP measurement could be developed to identify patients at risk of virologic failure, drug resistance for those on ART, and HIV acquisition for those on PrEP. As such, this novel pharmacological approach offers a unique opportunity to measure both PrEP and ART adherence.

This novel study demonstrates women’s decreased adherence to ART during the postpartum period using an objective pharmacologic measurement. We were able to follow most of this cohort (>85%) over time beginning in pregnancy or early postpartum through up to one year postpartum. A limitation of our study includes the inability to compare TFV-DP concentrations with HIV VL due to infrequent viral load testing in this cohort. Additionally, we did not collect data on psychosocial factors such as depression, intimate partner violence, and stigma that may contribute to poor adherence.61–63 Finally, our TFV-DP thresholds were developed in persons without HIV taking PrEP, who may exhibit different pharmacokinetics compared with our population of PWLWH (as previously demonstrated).15–17,57

Overall, these findings shed light on the cumulative longitudinal adherence patterns of women during pregnancy and into postpartum and identify opportunities for interventions to promote improved adherence. The use of TFV-DP in DBS as a measure of ART adherence in sub-Saharan Africa could be an important tool to optimize health outcomes for PWLWH and their infants.

Acknowledgements:

The authors would like to thank the women who participated in this study and acknowledge the contributions of the study and facility staff who carried out study activities. Additionally, we acknowledge the support of the Director KEMRI for and the University of Alabama at Birmingham (UAB) Center for AIDS Research (P30 AI027767) and the UAB Sparkman Center for Global Health in carrying out this work.

Sources of support:

National Institute of Child Health and Development R01HD080477

Footnotes

Data previously presented at the Conference on Retroviruses and Opportunistic Infections, Boston, Massachusetts, March 8–11, 2020.

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