Remarks

• In males and females, <30% of normal G6PD activity is considered deficient; females with G6PD activity between 30%and 70% due to a heterozygous genotype are considered to have intermediate G6PD activity and are also (but less so)at risk of haemolysis.
• In patients undergoing G6PD activity testing, near-patient semi-quantitative tests for G6PD deficiency with fixedthresholds corresponding to >30% and <70% of normal G6PD activity are considered highly accurate at a threshold of30% of normal G6PD activity to indicate whether P. vivax and P. ovale patients are G6PD deficient, and areconsidered accurate at a threshold of ≤ 70% activity to indicate whether P. vivax and P. ovale patients are deficient orhave intermediate G6PD activity.

Practical info Therapeutic pathways of P. vivax and P. ovale anti-relapse treatment with 8-aminoquinolines in relation to G6PD testing (see diagram below) In order to prevent relapses of P. vivax and P. ovale, and when the G6PD status of the patient was previously unknown, the following recommendations are made: A. If only a qualitative near-patient test for G6PD deficiency is available, tafenoquine single dose treatment or high dose primaquine (1mg/kg/day for 7 days) should not be given. If by the qualitative test the patient is classified as non-deficient primaquine should be used at a regimen of 0.5 mg/kg/day for 14 days or for 7 days. Since many heterozygous females will be classified as non-deficient by this type of test, precautions should be used (see Figure above). If the patient tests G6PD deficient, consider primaquine 0.75 mg/Kg once a week for 8 weeks under medical supervision and surveillance for haemolysis. B. If a semi-quantitative near-patient G6PD test is available: a. if the patient has G6PD activity > 70%, tafenoquine as single dose tafenoquine or high dose primaquine (1 mg/kg/day for 7 days or 0.5 mg/kg daily for 14 days) can be given; b. if the patient has intermediate G6PD deficiency between 30 and 70% tafenoquine should not be given; primaquine should be used at a regimen of 0.5 mg/kg/day for 14 days or for 7 days, with precautions; c. if the patient has G6PD activity < 30%, consider primaquine 0.75 mg/kg once a week for 8 weeks under medical supervision and surveillance for haemolysis. C. If G6PD testing is not available, a decision to prescribe or withhold primaquine should be based on the balance of the probability and benefits of preventing relapse against the risks of primaquine-induced haemolytic anaemia. This depends on the population prevalence of G6PD deficiency, the severity of the prevalent genotypes, the daily dose of primaquine and on the capacity of health services to identify and manage primaquine-induced haemolytic reactions. Tafenoquine should not be deployed if accurate G6PD quantitative or semi-quantitative testing is not available.