Situation: The nurse works at a Rural Health Unit (RHU) whose upland and lowland barangays are endemic for malaria, lymphatic filariasis, and schistosomiasis. A 28-year-old man has a positive rapid diagnostic test (RDT) for Plasmodium vivax. He is not severely ill, and his glucose-6-phosphate dehydrogenase (G6PD) status is not yet on record. According to the national malaria protocol, which plan is CORRECT?

P. vivax is treated with chloroquine plus a 14-day course of primaquine, which clears the dormant liver forms that cause relapse. Primaquine can cause hemolysis in G6PD deficiency, so G6PD status must be confirmed before the 14-day course is given. Artemether–lumefantrine with single-dose primaquine is the regimen for P. falciparum.

Clinical reasoning from the scenario

A 28-year-old man with a positive rapid diagnostic test for Plasmodium vivax needs radical cure, not just clearance of the blood-stage infection. The key decision point is that his G6PD status is unknown. In P. vivax malaria, the parasite leaves dormant liver forms called hypnozoites, which can reactivate weeks to months later and cause relapse. Chloroquine clears the acute blood-stage infection, but only primaquine eliminates hypnozoites and prevents relapse. However, primaquine can trigger severe hemolysis in patients with G6PD deficiency, so the national protocol requires confirming G6PD activity before starting the 14-day primaquine course. The correct plan is therefore to give chloroquine now and defer primaquine until G6PD results are available.

Why chloroquine must be started immediately

Chloroquine remains effective against the erythrocytic stages of P. vivax in most endemic areas, including the Philippines. Delaying chloroquine while waiting for G6PD results would leave the patient symptomatic and at risk of clinical deterioration. The blood schizonticide can be safely administered regardless of G6PD status because chloroquine does not cause oxidative hemolysis. The urgency is to control the acute parasitemia now; the radical cure with primaquine can follow once safety is confirmed.

The role of G6PD testing before primaquine

Primaquine is an 8-aminoquinoline that generates oxidative stress in red blood cells. In individuals with G6PD deficiency, the red cell cannot regenerate reduced glutathione efficiently, leading to hemolysis. The severity of hemolysis depends on the degree of enzyme deficiency and the primaquine dose. A systematic review of severe hemolysis during primaquine radical cure documented that hematological serious adverse events, including profound anemia and hemoglobinuria, occur predominantly in patients with unrecognized or unquantified G6PD deficiency ^[4]. Watch out! A normal G6PD qualitative test does not always exclude intermediate deficiency; quantitative testing is preferred when available. In this scenario, the patient’s G6PD status is not on record, so starting the 14-day primaquine course today would be unsafe.

Why option 1 is incorrect

Starting chloroquine plus 14-day primaquine today without knowing G6PD status violates the safety principle. The 14-day regimen delivers a higher cumulative primaquine dose than a single low dose, and the risk of severe hemolysis is dose-dependent ^[2][4]. In Latin America, where P. vivax relapse is a major barrier to elimination, the revised radical cure algorithm now mandates G6PD testing before selecting primaquine or tafenoquine ^[1]. The same logic applies in the Philippine setting: no 14-day primaquine without prior G6PD confirmation.

Why option 3 is incorrect

Chloroquine alone treats only the blood-stage infection. P. vivax is not simply a “milder” malaria; its hypnozoites cause relapses that can be clinically significant and contribute to ongoing transmission. Without primaquine, the patient may recover from the acute episode but experience recurrent parasitemia weeks later. Radical cure requires both drugs ^[2][3].

Why option 4 is incorrect

Artemether–lumefantrine plus a single low dose of primaquine is the first-line regimen for Plasmodium falciparum, not P. vivax. The single low-dose primaquine in that regimen acts as a gametocytocidal agent to reduce transmission of falciparum, not as a radical cure for vivax hypnozoites. Using artemether–lumefantrine for vivax would be an incorrect species-directed choice.

Comparison of regimens

Regimen	Target species	Purpose of primaquine	G6PD testing required
Chloroquine + 14-day primaquine	P. vivax	Radical cure (hypnozoite eradication)	Yes, before primaquine
Artemether–lumefantrine + single low-dose primaquine	P. falciparum	Gametocytocidal (transmission reduction)	Not routinely for single low dose
Chloroquine alone	P. vivax blood stage only	None	No

Dose considerations from the evidence

The optimal primaquine dose for P. vivax radical cure varies by region. A meta-analysis from Latin America found that higher total doses of primaquine improve anti-relapse efficacy but also increase gastrointestinal and hematological risks, particularly in patients with lower G6PD activity ^[2]. In Indonesia, where relapse patterns are diverse, higher-dose primaquine regimens were evaluated only in patients with G6PD activity ≥30%, reflecting the safety threshold used to minimize hemolysis risk ^[3]. These findings reinforce the principle that primaquine dosing must be individualized based on both regional relapse epidemiology and the patient’s G6PD status. In this Philippine scenario, the national protocol’s requirement to confirm G6PD before the 14-day course is consistent with the broader evidence base.

Nursing implications for the RHU setting

In a Rural Health Unit managing endemic malaria, the nurse’s responsibilities include ensuring that the RDT result is correctly interpreted, documenting the species, and coordinating G6PD testing before primaquine is dispensed. Key point! The nurse should not administer or dispense the 14-day primaquine course until the G6PD result is available and reviewed. Patient education should cover the importance of completing the full primaquine course once started, recognizing signs of hemolysis such as dark urine, jaundice, or sudden fatigue, and returning immediately if these occur ^[4]. The chloroquine component can be started on the same day as the RDT result, because it is safe regardless of G6PD status and addresses the acute infection without delay.