Which diagnostic test to use for Testing and Treatment strategies in Plasmodium vivax low-transmission settings: a secondary analysis of a longitudinal interventional study

Abstract

Background: The lack of sensitive field tests to diagnose blood stages and hypnozoite carriers prevents Testing and Treatment (TAT) strategies to achieve Plasmodium vivax elimination in low-transmission settings, but recent advances in Polymerase Chain Reaction (PCR) and serology position them as promising tools. This study describes a PCR-based TAT strategy (PCRTAT) implemented in Saint Georges (SGO), French Guiana, and explores alternative strategies (seroTAT and seroPCRTAT) to diagnose and treat P. vivax carriers.

Methods: The PALUSTOP cohort study implemented in SGO (September 2017 to December 2018) screened participants for P. vivax using PCR tests and treated positive cases. Serology was also performed. Passive detection of P. vivax infection occurred during follow-up. Participants were categorised into overlapping treatment groups based on 2017 PCR and serological results. Strategies were described in terms of participants targeted or missed, primaquine contraindications (pregnancy, G6PD severe or intermediate deficiency), and sociodemographic characteristics.

Findings: In 2017, 1567 inhabitants were included, aged 0-92 years. A total of 90 (6%) were P. vivax carriers and 390 seropositive (25%). PCRTAT missed 282 seropositive individuals while seroTAT would have missed 21 PCR-positive cases. Primaquine contraindications ranged from 12% to 17% across strategies.

Interpretation: Serology and PCR are promising tools for targeted treatment strategies in P. vivax low-transmission settings, when field compatible sensitive tests will be available. Both seem necessary to capture blood stages and potential hypnozoite carriers, while avoiding mass treatment. However, high primaquine contraindications rates need consideration for successful elimination.

Funding: Supported by European Funds for Regional Development, French Guiana Regional Health Agency, Pan American Health Organization, WHO, French Ministry for Research.

Keywords: Elimination; Low transmission; Plasmodium vivax; Relapse; Serology.

Fig. 1

Potential treatment groups upon alternative campaign strategy depending malaria status.

Fig. 2

Flowchart of the study.

Fig. 3

Consistency of biological results: repartition of participants RDT, PCR, and serological results and number of participants with primaquine contraindication (PQ CI) shown for each group. Interpretation: 90 participants were PCR positive: 67 seropositive and 23 seronegative or with missing serological results. Of the 90 PCR positive, 11 had contraindications to primaquine (12%). 390 participants were seropositive whatever their PCR result. Among all seropositive, whatever their PCR result, 50 had contraindications to primaquine (13%).