Procalcitonin as a biomarker for severe Plasmodium falciparum disease: a critical appraisal of a semi-quantitative point-of-care test in a cohort of travellers with imported malaria

Abstract

Background: Imported malaria occurs as a relatively rare event in developed countries. As a consequence, most clinicians have little experience in making clinical assessments of disease severity and decisions regarding the need for parenteral therapy or high-level monitoring. In this study, the diagnostic accuracy of procalcitonin (PCT) for severe Plasmodium falciparum disease was assessed in a cohort of 100 consecutive travellers with various species of imported malaria.

Methods and results: In all patients, PCT was measured on admission with a semi-quantitative 'point-of-care' test. Patients with severe P. falciparum malaria had significantly higher median PCT levels on admission as compared with patients with uncomplicated P. falciparum disease. In addition, PCT levels in patients with non-falciparum malaria were also higher compared with patients with non-severe falciparum malaria but lower compared with severe P. falciparum malaria. At a cut-off point of 10 ng/mL, PCT had a sensitivity of 0,67 and a specificity of 0,94 for severe falciparum disease. However, at lower cut-off points the specificity and positive predictive value were rather poor although the sensitivity and negative predictive value remained high.

Discussion: Potential drawbacks in the interpretation of elevated PCT levels on admission may be caused by infections with non-falciparum species and by concomitant bacterial infections.

Conclusion: Semi-quantitative determination of PCT on admission is of limited use in the initial clinical assessment of disease severity in travellers with imported malaria, especially in settings with limited experience with the treatment of malaria.

Figure 1

Procalcitonin (PCT) levels on admission in relation to parasite load in 71 patients with falciparum malaria. Bars represent the median value of each group. Arrow heads indicate the patients with severe falciparum malaria. Statistical analysis showed an overall statistically significant difference between the various PCT groups on admission (p = 0.0012). Post-hoc group-to-group analysis showed significant differences in parasite load (identified by the asterix sign *) between various PCT groups (Normal vs moderate, p = 0.0044; normal vs high, p = 0.0013; and low vs high, p = 0.0403, respectively).