Cost analysis of school-based intermittent screening and treatment of malaria in Kenya

There is a growing appreciation that malaria not only impacts on the health of infected individuals but also has broader social and economic consequences [1, 2]. Recent evidence suggests that non-severe malaria can affect the cognition, attention and ultimately educational achievement of school children [3‐7]. Reaching this population is most effectively achieved via the school infrastructure, and with increasing enrolment in schools by African school-age children [8], schools provide a natural access point for malaria control among this age group. Notwithstanding this potential, the optimal approach to controlling malaria in schools remains unclear [4, 9]. Recent studies in Africa have demonstrated the potential of intermittent preventative treatment (IPT) - the administration of curative doses of anti-malarial treatment at predefined intervals regardless of infection status - in reducing malaria parasitaemia, clinical disease and anaemia and improving cognitive performance [3, 10, 11]. Moreover, modelling work demonstrates that IPT administered among school-age children can also help reduce malaria transmission in the wider community, particularly in areas of low to moderate transmission [12]. However, recent changes in national drug policies in many African countries preclude the use of sulphadoxine-pyrimethamine and amodiaquine, some of the drugs previously used in IPT, thereby limiting its potential implementation.

An alternative school-based malaria control strategy is intermittent screening and treatment (IST), using rapid diagnostic tests (RDTs) to screen and treat asymptomatic children. Recent studies in Ghana found IST in pregnant women to be equally efficacious as IPT [13] and acceptable to patients [14]. The present analysis examines the costs of IST of school children in two districts in coastal Kenya as part of an ongoing trial investigating the impact IST has on the health and education of school children [15]. The analysis explores how variation in the design of the intervention, including different component prices, affects programme cost.

The total financial cost of providing a five-year programme of malaria screening and treatment to 3,685 children is estimated to be US$ 365,104 or US$ 6.61 per child screened. The economic costs of the programme are US$ 69,062 per year, US$ 6.24 per child screened or US$ 18.72 per child per year. Table 2 provides a breakdown of financial and economic costs. The largest single contributors to cost are salaries (36%) and RDTs (22%). Almost half (47%) of the intervention cost comprises redeployment of existing resources including health worker time and use of hospital vehicles. The new funds required are largely due to RDTs and other consumables, their distribution to local facilities and staff per diems. Table 3 presents the resource costs cross-tabulated against the intervention activities and shows that the majority of the costs are spent on screening (52%), then treatment follow-up (21%) and intervention administration (20%). Data from the health worker time surveys indicates that daily travel to and from the schools during screening took on average 3 hours 20 minutes or 47% of total time. Undertaking the screening and providing treatment took 3 hours 16 minutes (45%), with preparation in the schools taking 36 minutes (8%).

The current analysis estimates that the financial cost of IST is US$ 6.61 per child screened. The economic cost is US$ 6.24 although the difference is largely due to discounting of costs incurred in the future. The largest cost components were RDTs and salaries. Almost half (47%) of the costs comprised of the redeployment of existing resources including health worker time and use of hospital vehicles. While this may reduce the new funds required to finance the intervention it also highlights the potential for additional strain to be placed on existing resources, depending on the current working capacity. Sensitivity analysis highlighted that changes to the delivery strategy, such as using different RDTs, removing treatment follow-up and only including nurses in the screening team, can reduce overall costs by 40%, increasing the affordability of the intervention.

Although IST is principally a strategy of treatment rather than prevention of malaria, it can be compared to preventive interventions such as IPT in that it seeks to prevent malaria associated anaemia and its consequences in school children [3, 10]. Studies in western Kenya found the yearly cost of school-based IPT to be US$ 3.17 per child [18] (Unless otherwise stated costs are adjusted to US$ 2010 using national CPI). Notwithstanding inflationary differences, the yearly cost of three rounds of IST at US$ 18.72 per child is considerably higher than IPT. It should be noted however, that the low cost of IPT hinges on the ability to use SP or amodiaquine, which is no longer possible in Kenya due to changes in national drug policy withdrawing SP and amodiaquine monotherapy. The ACT dihydroartemisinin-piperaquine (DP) has been considered as an alternative for IPT in school children [11], but would increase IPT costs [18]. The cost of IPT for children (IPTc) aged between 1 and 5 years in Ghana is estimated to be US$ 11.38 to US$ 14.79 [19] while a comparison of strategies for delivering IPTc in the Gambia estimated costs of US$ 3.85 and US$ 1.81 if delivered by village health workers or reproductive and child health trekking teams respectively [25]. This illustrates the opportunities for cost reduction depending on delivery strategy and highlights the potential difference in cost between settings. Multi-site studies of IPT for infants (IPTi) and for insecticide-treated bed net (ITN) distribution found respective yearly costs to be in the region of US$ 1.36 to US$ 4.03 per child (US$ 2007) [26] and US$ 1.38 and US$ 1.90 per child (US$ 2005) [27]. Studies are also beginning to consider screening strategies for targeting asymptomatic malaria infection in the wider community [28, 29], although estimates of cost are not yet available.

The sensitivity analysis provides an indication of how the costs of IST may be reduced in the future. A variety of malaria RDTs are currently available, but have varying diagnostic performance and any cost savings in using different RDTs or an alternative diagnostic tool will need to be balanced against performance. In the current study, the cheaper RDT considered in the sensitivity analysis performs slightly better than the trial RDT according to studies by the World Health Organization [30]. RDT diagnosis performs similarly to or even better than routine microscopy in health centres [31], although a lower mean parasite density in asymptomatic infection may affect diagnostic performance. A study of school children with and without fever in Benin found that while PCR diagnosis led to a considerable increase in identified Plasmodium infection compared to microscopy or RDT, there was little or no clinical benefit in treating sub-microscopic infection [32]. Moreover, the costs of screening programmes using microscopy or PCR diagnosis would likely be prohibitively expensive. While cost-effectiveness of RDTs compared to microscopy in health centres depends on the local setting [33‐36], the logistical disadvantage of microscopy as a mobile diagnostic tool means it is unlikely to be cost-effective for school-based IST.

The change to unsupervised treatment is justified on (i) findings from previous clinical trials indicating that supervised treatment and unsupervised treatment are equivalent in terms of efficacy [37, 38] and (ii) that national guidelines permit unsupervised treatment [39]. In addition to the likely reduction in health worker personnel time on implementation, there may be scope for teachers to assist or even lead screening. Studies in Zambia and the Democratic Republic of Congo have shown that RDTs can be used effectively by non-medical personnel [40‐42]. The wider regional or national roll out of IST may result in reduced RDT cost from bulk purchasing and improved efficiency from familiarity with the intervention. However, as coverage expands to include those in more remote areas, increased transport and therefore personnel time may increase marginal cost. In addition, integration with other school-based or community health programmes provides further potential cost reduction through economies of scope. For example, school health programmes currently provide children with de-worming and micronutrient supplementation [43]. The UNICEF led Child Health Day programme can cost-effectively deliver multiple health services to younger children [44] and bed net distribution has been successfully integrated with routine or campaign vaccination strategies [45]. IST implementation would need to be tailored to the epidemiological context and take into account infrastructural capacity and local geography. The cost, and ultimately cost-effectiveness, will crucially depend on the prevalence of Plasmodium infection, with overall costs decreasing with decreasing prevalence but costs per child treated increasing exponentially. However, this does not incorporate potentially crucial cost savings associated with reducing malaria transmission. That is, this strategy may indeed be cost-effective at low to moderate prevalence if elimination, or even reduction in transmission, is achieved.

There are certain limitations associated with economic evaluations of randomized trials. In this case, the intervention is designed with the trial objectives in mind and not maximisation of cost-effectiveness, for example only two classes per school were screened. In the base case scenario all research only costs were removed but intervention alterations were not modelled. The intention is to maximize the level certainty in the base case estimate, providing a solid estimate of cost from which to model variation in setting or intervention design. Findings can be generalized for settings with similar social, economic and epidemiological conditions, such as Western or Nyanza provinces [16]. Although specific figures will change, options for cost reduction, issues around scale-up and discussion of consequences are likely to remain relevant. A degree of socio-economic, epidemiological and environmental consistency is assumed and the analysis does not account for significant exogenous variation. In particular, it is assumed that the prevalence of malaria remains constant year on year. It is noted that this is unlikely to be the case in the study setting since transmission is currently in decline [46].

In order to set the context of IST cost, the likely consequences of IST are identified through consideration of the trial outcomes and a review of the relevant literature (Table 5). The aetiology of anaemia and its interaction with malaria is complex but treating asymptomatic Plasmodium infection using IPT has been found to reduce anaemia by 48% in school children in western Kenya [3] and 47-56% in children under five years of age in Mali and Burkina Faso [47, 48]. Although IST targets asymptomatic infection there is likely to be an impact on the incidence of clinical malaria through the reduction of superinfection [49], whereby infection from an initial mosquito bite has not cleared before a second infectious bite occurs. There may also be a prophylactic effect of AL against new infection [50], an effect likely to vary according to drug choice. In addition to the benefits for individuals receiving IST, there may be effects on the wider community. In endemic regions, individuals with chronic asymptomatic infection, so-called asymptomatic carriers, are thought to represent a significant reservoir of Plasmodium transmission and treatment of such carriers can help reduce overall transmission in the community [51‐53]. Mathematical modelling of community-based screening and treatment and, separately, of IPT in school children highlight the potential for reducing malaria transmission in this way [12, 54]. Further to these effects, school-level estimates of infection prevalence derived from IST can help inform surveillance of malaria transmission [55], a key resource in disease control. Finally, by targeting asymptomatic infection, IST exposes a new section of the parasite population to an anti-malarial resistance selection pressure. Yeung et al describe the benefit of asymptomatic Plasmodium infections in suppressing the spread of drug resistance [56].

With regard to impact on malaria transmission, Kern et al [54] found that intermittent community screening campaigns using RDTs followed by treatment of asymptomatic carriers has greatest impact in areas of high transmission but that the rate of infection returned to its normal level in the subsequent year, unless the intervention was repeated, highlighting the potential of community-based IST in reducing malaria transmission. In areas of low transmission, the reduction in infection was sustained for over three years following a single round of intervention. The impact of screening and treating only school children on the overall level of transmission in the wider community remains to be established, but Aguas et al find that IPT in school children has the potential to reduce transmission particularly in areas of low or moderate endemicity [12]. Kern et al also found that screening campaigns scheduled in close succession (monthly intervals) at the start of the dry season had the greatest impact on the success of the intervention. Such findings have relevance for the optimal delivery of school-based IST.

In addition to the impact on health and malaria control, school-based IST has the potential to improve education and reduce household costs. Malaria is considered to impact children's educational achievement through reduced school attendance due to illness and through impaired concentration and cognition [3‐7]. Recent work by Chuma et al estimated the average cost to the household per episode of malaria in the study districts, Kwale and Msambweni, to be US$ 2.52 [57] [Jane Chuma, personal communication]. The above breadth of potential consequences of school-based IST necessitates that a broad perspective to economic evaluation is adopted. A possible approach is cost-consequence analysis (CCA), a framework which presents, but does not aggregate, multiple outcomes. Coast et al [58] and Williams et al [59] support CCA as a clear and comprehensive approach to economic evaluation whilst Weatherley et al [60] recommend a CCA framework be used in the evaluation of intersectoral costs and consequences.

This analysis shows that in the current setting IST in schools is a relatively expensive intervention, primarily due to the RDT costs and the follow-up visits to observe treatment on day 2 and 3. However, many of the costs represent redeployment of existing resources and future alteration in the design of the intervention can reduce costs by 40%. Future research will evaluate impact of IST in schools and how this might vary in different transmission and operational settings.