Malaria prevalence and performance of diagnostic tests among patients hospitalized with acute undifferentiated fever in Zanzibar

Abstract

Background Control efforts in Zanzibar reduced the burden of malaria substantially from 2000 to 2015, but re-emergence of falciparum malaria has been observed lately. This study evaluated the prevalence of malaria and performance of routine diagnostic tests among hospitalized fever patients in a 1.5 years period in 2015 and 2016. Methods From March 2015 to October 2016, paediatric and adult patients hospitalized with acute undifferentiated fever at Mnazi Mmoja Hospital, Zanzibar were included. The malaria prevalence, and performance of rapid diagnostic test (RDT) and microscopy, were assessed using polymerase chain reaction (PCR) as gold standard. Results The malaria prevalence was 9% (63/731). Children under 5 years old had lower malaria prevalence (5%, 14/260) than older children (15%, 20/131, p = 0.001) and persons aged 16 to 30 years (13%, 15/119, p = 0.02), but not different from persons over 30 years old (6%, 14/217, p = 0.7). All cases had Plasmodium falciparum infection, except for one case of Plasmodium ovale. Ten malaria patients had no history of visiting mainland Tanzania. The RDT had a sensitivity of 64% (36/56) and a specificity of 98% (561/575), and microscopy had a sensitivity of 50% (18/36) and a specificity of 99% (251/254), compared to PCR. The malaria parasitaemia was lower in patients with false negative results on RDT (median 7 × 103 copies/µL, interquartile range [IQR] 2 × 103 – 8 × 104, p = 0.002) and microscopy (median 9 × 103 copies/µL, IQR 8 × 102 – 7 × 104, p = 0.006) compared to those with true positive RDT (median 2 × 105 copies/µL, IQR 3 × 104 – 5 × 105) and microscopy (median 2 × 105 copies/µL, IQR 6 × 104 – 5 × 105). Conclusions The study emphasizes that malaria was a frequent cause of febrile illness in hospitalized patients in Zanzibar in the years 2015-2016, particularly among school age children and young adults. We found evidence of autochthonous malaria transmission in Zanzibar. Compared to PCR, both RDT and microscopy had low sensitivity, and false negative results were associated with low parasitaemia. While low parasitaemia identified only by PCR in a semi-immune individual could be coincidental and without clinical relevance, clinicians should be aware of the risk of false negative results on routine tests.

Comparison of Rapid Diagnostic Test, Microscopy, and Polymerase Chain Reaction for the Detection of Plasmodium falciparum Malaria in a Low-Transmission Area, Jazan Region, Southwestern Saudi Arabia

“…RDT reported in this study is similar to that reported for the CareStar Malaria p.f/p.v (Pf-HRP2/Pv-pLDH) combo test in low-transmission areas in Ethiopia [ 17 ]. However, previous studies in declining malaria transmission or pre-elimination settings demonstrated reduced performance of light microscopy and different Pf-HRP2-based or Pf-HRP2/pLDH combo RDTs [ 33 , 40 , 41 , 42 , 43 ]. On the other hand, a study in a low-transmission region of Senegal reported high sensitivity and specificity for the CareStar Malaria Pf-HRP2/Pv-pLDH combo RDT (97.3% and 94.1%, respectively) and microscopy (93.2% and 100%, respectively) compared with PCR [ 44 ].…”

Madagascar In-Country Evaluation for Bioline™ Malaria Ag Pf/Pan and Bioline™ Malaria Ag

“…The implications of missed infections are signi cant, as prompt and accurate diagnosis is crucial for timely treatment and preventing disease progression. Low parasitemia has been identi ed in other studies as a limitation when considering RDTs for malaria diagnosis [29]- [32]. False negatives detected by RDTs could potentially be attributed to pfhrp-2 gene deletions, mutations, or the prozone effect, as reported by other studies.…”

Knowledge, attitudes and practices towards malaria diagnostics among healthcare providers and healthcare-seekers in Kondoa district, Tanzania: a multi-methodological situation analysis

“…Considering the challenges of microscopy as a diagnostic tool for malaria in rural Tanzania, the substantial number of patients that tested positive with BFM would have exacerbated the number of incorrect malaria diagnoses and treatments prescribed together with the potentially false positive clinical diagnoses [17,18]. On the other hand, the relatively low proportion of malaria positive rates among the RDT tested individuals may contribute in fuelling concerns over the extent of false negatives that are still being observed on Mainland Tanzania and Zanzibar [50,51]. While not perceived a major immediate concern, it was stressed that clinicians should be aware of the risk.…”