Table 5. Results of Cox proportional hazards models for the effect of primaquine on the risk of re-presentation to hospital with P. vivax malaria within 3 months of being treated for P. vivax malaria.
Primaquine dose | AHR | 95% Confidence interval | p | |
---|---|---|---|---|
Overall model | ||||
Alla | None | 1.00* | – | – |
Low- or high-dose primaquine | 0.88 | 0.82–0.94 | <0.001 | |
Subgroup analyses | ||||
1 to <5 yrb | None | 1.00* | – | – |
≥5 mg/kg (high dose) | 0.82 | 0.75–0.89 | <0.001 | |
5 to <15 yrb | None | 1.00* | – | – |
≥5 mg/kg (high dose) | 0.94 | 0.77–1.16 | 0.579 | |
≥15 yrb | None | 1.00* | – | – |
≥5 mg/kg (high dose) | 1.03 | 0.90–1.17 | 0.672 | |
2007c | None | 1.00* | – | – |
≥5 mg/kg (high dose) | 0.82 | 0.75–0.91 | <0.001 | |
Primaquine dose ≥7 mg/kga | None | 1.00* | ||
≥ 7 mg/kg | 0.88 | 0.82–0.95 | 0.001 | |
Outpatientsd | None | 1.00* | – | – |
≥5 mg/kg (high dose) | 0.86 | 0.81–0.93 | <0.001 |
Note: Patients treated with blood schizontocides other than dihydroartemisinin-piperaquine, pregnant women, and infants less than 1 year of age were excluded from all the models. Abbreviations: AHR, Adjusted Hazard Ratio
* Reference category.
a Cox model stratified by ethnicity (non-Papuan, Highland Papuan, and Lowland Papuan) and age group (1 to <5 yr, 5 to <15 yr and ≥15 yr). Other co-variables include gender, year, admission status (outpatient or inpatient), and presentation number.
b Cox models stratified by ethnicity. Other co-variables include gender, year, admission status, and presentation number. Age group was found to be an effect modifier of the association between primaquine dose and vivax recurrence; p < 0.001 from likelihood ratio test comparing models with and without an interaction term between age group and primaquine dosing.
c Model limited to the period during and 12 months before and after the largest primaquine stock outage in 2007. Cox model stratified by ethnicity and age group. Other co-variables include gender, admission status, and presentation number.
d Cox model stratified by ethnicity and age group. Other co-variables include gender, year, and presentation number.