Vivax Malaria Clinical Trial
Official title:
G6PD Assessment Before Primaquine for Radical Treatment of Vivax Malaria
This will be a single-arm observational cohort study. Malaria patients with Plasmodium vivax
and meeting study inclusion criteria, who give consent to be enrolled in the study, will have
their G6PD status measured by the CareStartâ„¢ G6DP rapid diagnostic test (G6PD RDT), and
primaquine prescribed according to the result. According to the G6PD RDT result, primaquine
will be prescribed at 0.25mg/kg/day for 14 days (normal patients) or 0.75mg/kg weekly for
eight weeks (deficient patients). All will receive treatment with chloroquine to clear
asexual stages of infection.
Patients will be reviewed at day 2, day 7 and day 14. At these visits patients will undergo a
brief clinical assessment and a small blood sample will be taken for repeat haemoglobin
measurement and dried blood spot for carboxyprimaquine measurement (day 7 and day 14 only).
In general, antimalarial treatment will be unsupervised to reflect field conditions. However
a subset of 25 G6PD normal patients at a single site will have each day of their primaquine
treatment administered and observed at the treatment centre. This is to determine a
calibration curve for primaquine pharmacokinetic studies.
Dried blood spots will be stored appropriately. Day zero samples will be genotyped in Bangkok
(MORU, Dr. Mallika Imwong) after DNA extraction. PCR-RFLP will be used to detect the allele
associated with the Mediterranean variant of G6PD deficiency. In addition DNA extracts will
be sent for more systematic genetic testing for known G6PD variants through existing
collaborations with the Wellcome Trust Sanger Institute. The day 7 and 14 dried blood spot
samples will be analysed in the MORU pharmacology laboratory for primaquine and
carboxyprimaquine concentrations, from which adherence to primaquine can be determined
retrospectively, using the subset of 25 patients receiving directly observed therapy to
calibrate the results.
Funder: WellcomeTrust, Grant reference: 107548/Z/15/Z
1. Screening All patients registering for outpatient services in the outpatient department
will undergo routine investigation. When malaria is suspected, a thick and thin blood
smear will be obtained for microscopic diagnosis of Plasmodium vivax or a malaria RDT
undertaken. After the diagnosis is confirmed microscopically, an assessment will be made
to see if the patient fulfils the study inclusion and exclusion criteria.
The following clinical screening procedures will be performed. The age, gender, ethnic
group, and contact details of the subject will be recorded in the source documents. In
the medical history, any history of chronic disease including previous history of
haemolysis or anaemia will be noted along with a history of allergy to any medications
(including chloroquine or primaquine).
Pregnancy is a contraindication to primaquine and all women considered at risk of
pregnancy will undergo urine pregnancy testing prior to enrolment. A pregnancy test is
done routinely in Afghanistan, consistent with National Treatment Guidelines.
Vital signs (axillary temperature in degrees Celsius, heart rate, respiratory rate,
blood pressure, and weight in kilograms) will be recorded. The physician will perform a
general systems examination.
2. Consent Patients who fulfil the study inclusion and exclusion criteria will be
approached for informed consent.
3. Procedures after enrolment
Once informed consent is given, a second capillary blood sample (finger prick) will be
taken for:
- CareStart RDT G6PD test. The RDT will be read at the appropriate time (10 minutes)
and the result noted in the source documents. The RDT itself will be labelled and
retained for future reference. It can also be analysed for host and parasite
genotypes.
- Baseline haemoglobin measurement via the HemoCue system. This will generally
involve use of a micropipette and the HemoCue microcuvettes.
- Collection of a dried blood spot (FTA card) labelled with an individual barcode.
- If a malaria RDT was used for diagnosis this will also be labelled and kept if
possible for future analyses of G6PD and parasite genotyping.
- Biosensor recordings will also be made in a subset of patients at day 0 and day 14,
if and when the device becomes available. These results will not influence patient
management which will be based only on the RDT result.
4. Antimalarials Chloroquine will be provided aiming for a dose of 10 mg/kg on day 0 & 1
and 5mg/kg on day 2, (Afghanistan NMLCP guidelines).
Primaquine will also be provided. (See dosing tables below) The target dose of
primaquine is:
- 0.25 mg/kg/day for 14 days (G6PD normal patients)
- 0.75 mg/kg weekly for eight weeks (G6PD deficient patients). For small children,
accurate drug dosage will be ensured by crushing a whole 15mg tablet and mixing in
10 ml water (with sugar if possible) prior to oral administration of 1-4 ml via a
syringe (see Table 2). For older children and smaller adults tablets will be split
to the nearest quarter (see Appendix these doses can also be crushed for
administration if necessary).
Primaquine daily dosing This dosing table provides a daily dose of between 0.19 and 0.33
mg/kg primaquine (total dose over 14 days 2.6 - 4.7 mg/kg).
Children will be offered sweet drinks once the drug been administered to minimize the
chance of vomiting. Parents of children will be shown how to measure the dose to allow
accurate home administration.
Treatment will generally be unsupervised to reflect field conditions. Sufficient
primaquine will be given to last until the next visit. From the investigators own work
and that of others in a similar population, adherence in this population is good, but
this will be checked by pharmacological assessments of carboxyprimaquine levels.
A subset of 25 G6PD normal patients at one site will have their primaquine treatment
observed each day at the treatment centre by a qualified member of the staff designated
by the principal investigator. Study patients will be observed for 60 minutes after drug
administration for vomiting. Any patient who vomits during the first half-hour
observation period will be retreated with the same dose of drug and observed for an
additional 30 minutes. If the patient vomits in the second period they should receive
half the drug. This will simply be noted and no further doses of primaquine given that
day; doses will be given from the next day onwards as normal. A slightly extended case
record form (CRF) will be used to record the timing of administration of primaquine
doses in a tabular format.
5. Patients with G6PD deficiency discovered at baseline Patients judged to be G6PD
deficient will receive counselling in terms of what the diagnosis means, how they should
avoid certain drugs and to show the G6PD card every time they buy drugs from a
pharmacy/drug store or visit their doctors. They will be provided with a G6PD deficiency
card listing drugs they should avoid.
6. Follow-up Prior to going home on day 0, Patients will also be provided with clear verbal
instructions in terms of self-monitoring for features of haemolysis, and advised to
attend if any of these occur. All patients will be advised to return if they experience
any side-effects. The Patient Information Sheet explains this and specifically refers to
the symptom of dark urine.
The patient will re-attend for follow-up at day 2, day 7 and day 14 and the following
information recorded
- Medical and medication history
- Physical examination including vital signs
- Capillary blood sample (finger prick)
- Haemoglobin measurement
- Dried blood spots (d7 and d14) for primaquine and carboxyprimaquine.
- Day14 G6PD activity measured by the Biosensor (subset of patients)
- Adverse events assessment focussing on patients who require hospitalisation
7. Haemolysis and stopping primaquine Based on the extensive work already undertaken on the
G6PD RDT, and with appropriate care, primaquine-induced haemolysis should not be a
significant problem in this study. However, it is important to stop primaquine in
individuals with signs of haemolysis, whatever the result from the initial G6PD RDT.
Haemolysis is likely to manifest itself as early as first 48 hours after commencement of
primaquine. The main symptoms are dark urine (macroscopic haemoglobinuria) and weakness /
tiredness due to an acute fall in haemoglobin.
The following criteria will be used to define an episode of haemolysis that requires
primaquine to be stopped (and not reintroduced):
- Either a drop in haemoglobin concentration by more than 2g/dl compared to baseline
- Or an absolute haemoglobin concentration of less than 7 g/dl at any time The healthcare
worker may also stop primaquine administration for reasons outside these criteria. If
necessary patients will be admitted for management, or referred / transferred elsewhere,
as per local practice.
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