Study participants are recruited in different ways, participation in the study is offered when attending an asylum health clinic at several sites in the Stockholm county. Secondly, patients attending the Infectious Disease outpatient clinic for non-febrile diseases (e.g. follow up of hepatitis, treatment for latent tuberculosis). Thirdly, quota refugees from Democratic Republic of the Congo or Uganda with arrival in Sweden in the years 2015-2019 with postal address in Stockholm, will be invited by letter to participate in the study .
A venous blood sample (EDTA tube) is collected from study participants at one occasion and a questionnaire including questions about patient origin and previous malaria are completed with the aid of a translator.
Blood samples are analysed in the research laboratory, where a malaria rapid diagnostic test (RDT) is performed and haemoglobin concentrations are measured (using Hemocue, point of care test) the same day as sample collection. The samples are then centrifuged, aliquoted, and stored frozen at the research laboratory. Presence of malaria parasites are analysed by realtime-PCR of the species specific 18SRNA gene in a multiplex assay. Serologic markers for other parasitic diseases (eg. schistosomiasis and strongyloides) are analysed in plasma. These analyses are performed at the reference laboratory at the Public Health Agency of Sweden.
Projected sample size is estimated using the formula n=(Z\^2xP(1-P))/d\^2 where P is the expected prevalence based on previous studies (5%) and d is the precision (1.5%) and Z is the confidence interval (95%). Based on these assumptions, the required sample size is n=715.
All RDT or PCR positive individuals are referred to the Department of Infectious Diseases or the Department of Pediatrics at the regional hospital for further investigations and treatment. Results from complete blood count are assessed and followed up according to clinical routine at each centre where samples were collected. Contact information to the study participant are included as part of the recruitment and consent procedures in order to be able to contact the study participants for referral.
Moreover, antibody responses to crude parasite extracts and specific antigens are assessed by ELISA and Luminex. In a subset of participants peripheral blood mononuclear cells, PBMC, are prepared in follow up samples to assess the cellular immune response. The magnitude and breadth of antibody and cellular responses are assessed in relation to duration of residency in a malaria free country. An estimation of the long- term decay kinetics using a sero-epidemiological mathematical model is performed.
All data will be handled according to the EU GDPR (General Data Protection Regulation) superseded all EU member states' data protection laws based on the 1995 Data Protection Directive (DPD), (GDPR, EU 2016/679 and SFS 2018:218). The patient register, containing all collected data and analysis results, is kept pseudonymizised and stored in a secure server at Karolinska University Hospital. The key to pseudonumization is kept in a secure locker at the institution.
Collected blood specimens are stored in Stockholm Medical Biobank located at Karolinska University Hospital in Solna. Handling of these stored samples is governed by the Act on Biobanks in Health Care (SFS 2002: 297).
