Stuckey EM, Ross A, Smith T

In the Perspective published in PLoS Medicine [1], von Seidlein notes the lack of impact seen in the recent cluster-randomized trial of school-based intermittent screen and treat (IST) for malaria in the south Kenyan coast [2], and observes that the investigators ‘consulted’ two mathematical models [3, 4], giving the reader the impression that over-optimistic predictions from mathematical models was a driver behind the testing of an intervention that proved ineffective.

In fact, both these modelling studies report simulations of mass screen and treat (MSAT) interventions to the whole population. They suggest that MSAT programs, even in favourable settings, must achieve very high coverage of the total population sustained at high frequency if they are to result in a worthwhile impact on infection rates. The prediction of limited impact on infection from screen and treat at operationally feasible frequency and coverage levels has now been borne out by field trials in Burkina Faso [5], and Kenya [2]. By treating only school-aged children once per term, the intervention described in Halliday et al [2] is substantially different from any supported by the cited modelling studies.

Mathematical models should indeed be used to decide in advance which interventions to test in the field. Using models to work out exactly what to test would make it more likely that trials will lead to improvements in public health practice. This should entail modelling realistic coverage and deployment options in settings comparable to those in the field.

References

1. von Seidlein L: The Failure of Screening and Treating as a Malaria Elimination Strategy. PLoS Med. PLoS Med 2014, 11:e1001595.
2. Halliday KE, Okello G, Turner EL, Njagi K, Mcharo C, Kengo J, Allen E, Dubeck MM, Jukes MC, Brooker S: Impact of Intermittent Screening and Treatment for Malaria among School Children in Kenya: A Cluster Randomised Trial. PLoS Med 2014, 11:e1001594.
3. Griffin JT, Hollingsworth TD, Okell LC, Churcher TS, White M, Hinsley W, Bousema T, Drakeley CJ, Ferguson NM, Basanez MG, Ghani AC: Reducing Plasmodium falciparum malaria transmission in Africa: a model-based evaluation of intervention strategies. PLoS Med 2010, 7.
4. Kern SE, Tiono AB, Makanga M, Gbadoe AD, Premji Z, Gaye O, Sagara I, Ubben D, Cousin M, Oladiran F, et al: Community screening and treatment of asymptomatic carriers of Plasmodium falciparum with artemether-lumefantrine to reduce malaria disease burden: a modelling and simulation analysis. Malar J 2011, 10:210.
5. Tiono AB, Ouedraogo A, Ogutu B, Diarra A, Coulibaly S, Gansane A, Sirima SB, O'Neil G, Mukhopadhyay A, Hamed K: A controlled, parallel, cluster-randomized trial of community-wide screening and treatment of asymptomatic carriers of Plasmodium falciparum in Burkina Faso. Malar J 2013, 12:79.