A Comparison Between Microscopy And Rapid Diagnostic Test Among Children 10-15 Years At Onitsha General Hospital, Anambra State

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A Comparison Between Microscopy And Rapid Diagnostic Test Among Children 10-15 Years At Onitsha General Hospital, Anambra State


Abstract


This study centres on a comparison between microscopy and rapid diagnostic test among children 10-15 years at Onitsha General Hospital, Anambra State. The study was conducted between the month of July and August. Geimsa thick film and Rapid Diagnostic Test were used to detect malaria parasite in the blood. A total of 150 participants comprising of 68(45.3) males and 82 (54.78) females selected from patients referred for malaria tests at General Hospital Onitsha Participants were aged 10–15 years. The prevalence of malaria in the study area was 26.7% for microscopy and 22.0% for rapid diagnostic test. Males were more infected with a prevalence rate of 14.7% (microscopy) and 11.3% (RDT) than with females a prevalence rate of 12.0% (Microscopy) and 10.7% (RDT). The difference in prevalence was not significant (p=0.610). Malaria prevalence in relation to age in the study shows that children within the age of 10 has the highest prevalence which decrease with the increase in years with the least prevalence been those with 15 years of age. Result shows that the use of microscopy is more reliable than the use of RDT. However, it is recommended that only the antigen based method kits be imported and, or used in Nigeria.


Chapter One


Introduction

1.1 Background Information

Malaria is a disease of the tropics and sub-tropics and is transmitted by a vector, female Anopheles mosquito. It is caused by Plasmodium (P.) falciparum, P. malariae, P. ovale and P. vivax. In Nigeria, the prevalent species is Plasmodium falciparum accounting for >90% of all diagnosed cases (95-98%), P. ovale (<2%), P malariae (2-5%) while P. vivax is not endemic in Nigeria. The dominant vector species are Anopheles (An) gambiae s.l. and the An. Funestus(Molta, 2003; 2004; FMH, 2008).

Malaria is a public health problem in Nigeria and accounts for 110 million clinically diagnosed cases per year. The disease is responsible for about 60% outpatient care-visits and 30% hospitalizations. At least 300,000 children die of malaria per year in Nigeria and up to 30% childhood deaths, 25% of deaths in children under one year and 11% maternal deaths are due to malaria (Federal Ministry of Health, 2005; United Nations Children Fund, 2010). It is estimated that 50% of the population will have at least one episode of malaria annually, with 2-4 episodes in under-5 year old children (Federal Ministry of Health, 2008). An estimated N132 billion is lost due to malaria annually in form of treatment costs, prevention, loss of man hours (Federal Ministry of Health, 2005; United Nations Children Fund, 2010). In 2008; 9,591 deaths were reported out of 3,481,220 reported cases of malaria in Nigeria, giving a Case Fatality Rate of about 0.3% compared to 0.2% in 2001 (Federal Ministry of Health, 2010). On a global scale, in 2008 there was an estimated 243 million cases of malaria worldwide with the majority of cases (85%) in the African Region, followed by the South-East Asia (10%) and Eastern Mediterranean Regions- 4% (World Malaria Report, 2009).

Over-prescription of antimalarial medicines is a very common phenomenon because the diagnosis of malaria is often presumptive, despite recommendation of routine laboratory diagnosis of malaria by the World Health Organisation (WHO) (Reyburn, Mbakilwa, Mwangi, Mwerinde, Olomi, Drakeley, Whitty, 2007). The use of laboratory methods has become necessary because health workers cannot identify malaria cases reliably using clinical signs and symptoms alone (Perkins, Zucker, Otieno, 2007; Weber, Mulholland, Jaffar, Troedsson, Grove, Greenwood, 2007). Conventional light microscopy of a blood smear is the reference gold standard for the detection of malaria parasites and the established method for the laboratory confirmation of malaria. It is sensitive and can detect densit ies as low as 5–10 parasites/µL of blood when used by skilled and careful technicians, (World Health Organization, 2000) but realistically at 100 parasites/µL under field conditions (World Health Organisation, 2008). Microscopy provides information on parasite species (P. falciparum, P. vivax, P. ovale, and/or P. malariae) and their circulating stages (e.g. trophozoites, schizonts, gametocytes). It aids quantification of the parasite densities and assessment of parasitological response to chemotherapy in severe malaria cases. It can provide a permanent record (the smears) of the diagnostic findings and be subjected to quality control. However, malaria diagnosis based on microscopy is labour-intensive and time-consuming, requiring at least 60 minutes from specimen collection and availability of result. Long delays occur in providing microscopy results to the clinician and as such, decisions on treatment are often taken without the benefit of the results (World Health Organisation, 2000). Microscopy depends absolutely on good techniques, reagents, microscopes and, most importantly, well trained and well supervised technicians. These conditions are hardly met at the more peripheral levels of the health care system making microscopic diagnosis an unreliable tool.

Rapid diagnostic tests (RDT) are recommended by WHO to enhance diagnosis and management of cases, prevention of complications of delayed treatment, prolonging survival and monitoring of treatment especially in children. Moreover, studies have shown that it is acceptable both to the practising physicians and the patients (Reyburn, Mbakilwa, Mwangi, Mwerinde, Olomi, Drakeley, Whitty, 2007). It is timely for case management of malaria and avoids the drawbacks of defective microscope and erratic power supply (Reyburn et al, 2007). It aids selective treatment of only patients with positive dipstick results and thus slows down the development of drug resistance by preventing drug pressure (Rimon, Kheng, Hoyer, Thach, Ly, Permin, and Piechie, 2003). Health workers with minimal skills can be trained in RDT techniques within periods varying from three hours to one day.(World Health Organisation, 2000), (Banchongaksorn, Prajakwong, Rooney, and Vickers) RDT is robust, non- cold chain dependent and the degree of variability of test reliability and performance among individual users is relatively small.(World Health Organisation, 2000) The specificity and sensitivity of 97% and ≥95% respectively have been shown, for self-diagnosis among travellers from endemic areas returning to United Kingdom and in remote areas of Philippines (Whitty, Armstrong and Behrens, 2000; Bell, Go, Miguel, Walker, Cacal, Saul and 2001).

Malaria RDT detects serum antigens of Plasmodium species using fixed antibodies on strips of paper. There are three types of newly developed RDTs on the WHO pre-qualified list. According to WHO, Plasmodium Lactate Dehydrogenase (pLDH) based-tests can detect all the Plasmodium species that infect humans.(World Health Organisation, 2000) They can distinguish P. falciparum from the non- falciparum species, but cannot distinguish between P. vivax, P. ovale and P. malariae (i.e. specific for P. falciparum). Some tests detect Aldolase antigens of Plasmodium malariae, ovale and vivax or specifically that of P. falciparum while others detect Plasmodium falciparum Histidine-Rich Protein II (HRP 2) antigen (Rock, Marsh, Saul, Wellems, Taylor, Maloy and Howard, 2007; Meier, Dobeli, and Certa, 2002; Makler, Piper and Milhous, 2008). Other antigen(s) that are present in all four species are also targeted in kits that combine detection of the HRP-II antigen of P. falciparum together with that of an, as yet unspecified, “pan-malarial” antigen of the other species (World Health Organisation, 2000). The choice of RDT depends on the malaria endemicity and species prevalence (Jimoh, 2006).

In 2009, WHO recommended that persons of all ages with suspected malaria cases should undergo rapid diagnostic tests, but only 18 of 35 countries reported adhering to this (World Malaria Report, 2009). In 18 malaria high-burden African Region countries for which data were available, 22% of the reported suspected malaria cases were confirmed with RDT in 2008 (World Malaria Report, 2009). The validity of some RDTs has been investigated over the years and has been shown to be of high specificity and sensitivity in comparison to light microscopy (Bell et al,2001; Bell et al,2005). The WHO recommends a sensitivity of ≥95% at ≥100 parasites/µl for P. falciparum. (World Health Organisation, 2000; Bell et al, 2005). Despite this recommendation and the reported validity of RDT, recent field and clinical-based studies indicated a low specificity and sensitivity compared with routine microscopy. The reasons alluded to were low parasitaemia, defective and inappropriate handling of RDT kits (World Malaria Report, 2009). The National Malaria programme has commenced the “roll out” of rapid diagnostic tests in some health facilities across the country, with the aim of scaling up its use in the field, where there is lack of skilled laboratory scientists and less than optimal conditions for routine microscopy. The recent trend of increasing mortality due to malaria in the general population and in high risk groups of pregnant women and children under the age of 5 years necessitates a more rapid scale up of malaria RDT (Federal Ministry of Health, 2010).

There is a high incidence of malaria in Nigeria with variability in endemicity. The southern part of Nigeria and the lower part of the northern region are associated with endemic and perennial episodes (7-12months). Transmission is endemic and seasonal (4-6months) in the upper north and epidemic or strongly seasonal in the extreme north-eastern part of the country (Federal Ministry of Health, 2008). The proportion of malaria confirmed by laboratory diagnosis in Nigeria is unknown. Diagnosis of malaria is often clinical-based and unreliable (Reyburn et al, 2007). This could lead to over diagnosis, inappropriate treatment and potential development of drug resistance. The use of routine laboratory microscopy to aid clinical diagnosis is minimal. However, the use of malaria rapid diagnostic tests is a new approach and its implementation is restricted to a few facilities in the country. Artemisinin-based combination therapy, the currently recommended treatment for malaria though efficacious, is costly. There is an urgent need to prioritise its use for cases that are purely due to P. falciparum because of possibility of potential development of drug resistance.


1.2 Aims of the Study

This study therefore aims to conduct a comparative study between microscopy and rapid diagnostic test among children between 10-15 years in Onitsha Anambra state.


1.3 Specific Objectives

Specifically, this study aims to;

  1. Ascertain the prevalence of malaria among children within the age 10-15 years in Onitsha South Local Government Area.
  2. Find out the predictive value of malaria rapid diagnostic test in relation to routine light microscopy.

Chapter Five


Conclusions and Recommendations

5.1 Conclusions

The overall prevalence of Plasmodium species infection at General Hospital, Onitsha during baseline study, first, second and third follow-ups were 10.5%, 2.6%, 5.5% and 11.4% respectively. Higher prevalence (10.5%) was recorded during the dry season (January to March) which coincided with the baseline survey and which was preceded by short rains in the months of October, November and part of December. The riverine ecological zone recorded highest overall prevalence (22.8%) followed by highland (1.9%), lowland (0.6%) and lastly by midland which had no cases of infection. Plasmodium species infection within riverine zone seemed to be perennial and not seasonal with highest prevalence (22.8%) occurring during dry season followed by short rainy season in October/ November (11.4%) and lastly during long rainy season in June/ July (6.5%). The proportion of asymptomatic P. falciparum infections was relatively higher within the riverine zone compared to other zones.

The overall risk of Plasmodium species infections in the study area was 5 in every 1000 persons per month. However, the risk of infection in riverine zone was 14 per 1000 persons per month.

The study showed that the performance of the three RDT kits in diagnosis of P. falciparum infections was relatively adequate and can be used in guiding treatment of febrile illness in remote settings especially where microscopy may be a challenge. SD Bioline Ag-Pf/Pan performed slightly better than CareStart Pf however, the difference was not statistically significant. Both SD Bioline Pf and CareStart Pf had similar test results. The three RDT kits had high negative predictive values indicating they can be reliably rule out the possible Plasmodium species infection. However, the low positive predictive values shows that individuals may be falsely diagnosed as positive by RDTs hence confirmation of the positive tests by microscopy to avoid unnecessary treatment.


5.2 Recommendations

  1. There is need for expanded malaria control strategies especially within the riverine zone which had the highest P. falciparum infections.
  2. Mass screening within the riverine zone should be considered to target the asymptomatic individuals for treatment in order to limit development of severe malaria. This would also lower transmission rates by reducing parasite load in the population. This can be done by Ministry of Health and other stakeholders.

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