Page 227 - SAHCS HIVMed Journal Vol 20 No 1 2019

Page 2 of 6 Original Research

which concentrations of EFV in hair were shown to be strongly a day during the study was classified as an adherent day, and
correlated with 24-h intensive pharmacokinetic measurements cumulative adherence was calculated as the number of
and only weakly correlated with single plasma measurements. adherent days divided by the number of days in care.
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Plasma EFV concentrations are characterised by high inter-
individual variability in concentrations, which can be Blood was drawn for HIV-1 viral load (HIV-1 RNA 3.0
explained, in part, by polymorphisms in the CYP2B6 gene that assay®; Bayer Healthcare, Leverkusen, Germany) at
has been reported to influence EFV metabolism. High plasma screening and at weeks 16 and 48. Additional blood was
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EFV concentrations have been associated with central nervous drawn for mid-dosing interval EFV concentrations (in the
system side effects, which can lead to patients discontinuing time window between 9 h and 16 h after self-reported EFV
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treatment. Hair concentrations of EFV are also influenced by intake) at weeks 16, 32 and 48. Three CYP2B6 loss-of-
CYP2B6 genotype. 14,15 function single-nucleotide polymorphisms associated with
EFV concentrations were chosen and analysed: rs3745274
This study is a supplementary to our recently reported (516G→T); rs28399499 (983T→C); and rs4803419 (15582C→T).
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randomised controlled trial of an adherence intervention Based on their CYP2B6 genotype, participants were
and investigates the potential of measuring EFV concentrations classified as either slow, intermediate or extensive
in hair to monitor adherence. In addition to determining the metabolisers using a simplified version of Holzinger’s
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effect of CYP2B6 metaboliser status on hair EFV concentrations, metaboliser status classification.
the relationship between plasma and hair EFV concentrations
will be assessed. Lastly, the relationship between the For the determination of EFV concentrations, blood samples
adherence measured by an electronic adherence monitoring were centrifuged at 3500 rpm for 10 min. Plasma was
device (EAMD) and hair EFV concentrations will be explored. transferred into labelled cryovials that were frozen at -80 °C
until analysis. Plasma EFV concentrations were determined
Methods by a liquid chromatography/tandem mass spectrometry
Setting and participants (LC-MS/MS) method validated for the concentration range
0.0195–20 µg/mL. Hair samples, collected at weeks 16, 32
The parent study was a randomised controlled trial over 48 and 48, were analysed at the same laboratory for EFV using a
weeks in ART-naïve individuals, which showed that SMS validated LC-MS/MS method. The method was validated
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reminders triggered by real-time EAMD had little impact on for the concentration range 0.625–40 ng/mg. The centimetre
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cumulative adherence to ART. Participants were recruited of hair closest to the scalp was analysed to represent drug
from a large outpatient ART centre in Gugulethu, Cape exposure of approximately one month.
Town – the Hannan Crusaid Treatment Centre (HCTC). ART-
naïve adults and adolescents (≥ 15 years old) were eligible for Statistical analysis
the parent study if they were commencing treatment at the
HCTC, had their own mobile phone and were willing to sign Descriptive data were summarised using median and
an informed consent form. The details of the parent study interquartile range (IQR) for continuous data and percentages
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have been described elsewhere. 16 for categorical data. The Χ test was used to compare
proportions, and the two-tailed t-test (for normal variables)
or the Mann–Whitney test (for skewed variables) was used to
Sub-study design and participants
compare continuous variables. GraphPad Prism 4 (California,
Participants recruited for the parent study were given the USA) was used for the statistical analysis of data, including
option of participating in the sub-study if the hair on their Spearman’s correlation. Regression modelling was used to
head was longer than 1 cm. The participants involved explore whether EFV hair concentrations were associated
provided samples of hair at weeks 16, 32 and 48. with the adherence measured using the EAMD and
virological outcome. Sex, baseline CD4 cell count, metaboliser
Measures and analyses – Laboratory procedures status and age were included as independent variables.
Samples that were determined to be below the assay methods
The measures collected for the parent study and the limit of quantification were analysed as 0.624 ng/mg for
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previously reported pharmacokinetic and pharmacogenetic EFV concentrations in hair and 0.0194 µg/ml for EFV
sub-study are described subsequently. In the parent study, concentrations in plasma.
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adherence was monitored using a Wisepill® device, a real-
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time EAMD. In a related study, the EAMD was shown to be Ethical consideration
the best adherence measure to predict virologic outcomes.
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The EAMD is of the size of a mobile phone and can store up to Ethical approval for the study was given by the University of
a week of medication in a seven-compartment pill box. Every Cape Town, Faculty of Health Sciences, Human Research
participant received an EAMD, and when each time the device Ethics Committee (HREC/REF: 101/2015). Informed consent
was opened, a signal was sent via the mobile phone network was provided by each of the study participants. The parent
to a secure central computer, thereby recording tablet taking or clinical trial was registered in the Pan African Clinical Trials
treatment interruptions in real time. Any recorded opening on Registry (number PACTR201311000641402).

http://www.sajhivmed.org.za 220 Open Access