Diagnosis of malaria during chloroquine/proguanil prophylaxis

Imported malaria: presentation and outcome of 111 cases

“…It is estimated that 50% of patients use effective chemoprophylaxis [8,9]. It has been suggested that chemoprophylaxis was associated with less frequent severe malaria and delay in presentation [8], and could lower parasitemia or modify parasite morphology [10]. However, like another report [11], we found that prophylaxis, even adjusted for compliance, did not modify clinical presentation or mean parasitemia.…”

The utility of serial blood film testing for the diagnosis of malaria

“…Plasmodium falciparum accounted for the majority of total cases of malaria in Queensland; 98% of these cases were diagnosed on the first blood film examination. 9 Prophylactic treatment has been implicated in false-negative thin blood films, and thick films with altered or atypical shaped parasites with very low parasite counts. These results are similar to the Victorian study that found P. vivax accounted for the majority of malaria cases with an initial negative blood film and rapid diagnostic test result.…”

“…In the group of patients who had an initial negative blood film result followed by a positive result, P. vivax was the most common malaria species, accounting for 78% of these cases. 9 These factors make it more difficult to diagnose malaria on blood film and may explain the higher prevalence of an initial negative blood film result in patients on prophylaxis. 6 The patients who have an initial negative result and subsequent positive films may not be random; the majority (55%) of these patients were members of the ADF.…”

Prolonged malaria prophylaxis with chloroquine and proguanil (chloroguanide) in a nonimmune resident population of an endemic area with a high prevalence of chloroquine resistance

“…More recently, in a survey of 100 consecutive patients with malaria living in the city of Yaounde, in vitro chloroquine-resistant strains of P. falciparum were found in 53 of the patients, while in 13 of them amodiaquine resistance was present. A decrease in susceptibility to mefloquine was also detected in two of the examined strains (9).…”

“…Although no differences in clinical presentation or incidence of complications were observed between the two groups, a significantly lower parasite count in the Ch-P-treated group was the rule. Technical difficulties in the light microscopy diagnosis of malaria because of low parasitemias were frequently encountered by experienced laboratory technicians, and malaria parasites were missed since an altered parasite morphology was often associated with Ch-P prophylaxis (12). Reliance upon disease symptoms only would impinge on diagnostic accuracy and cause overtreatment.…”