The present review protocol is being reported in accordance with the reporting guidance provided in the Pre-ferred Reporting Items for Systematic Reviews and Meta- Analyses Protocols (PRISMA-P) (see PRISMA-P checklist in Additional file 1). This review protocol has been registered within the International Prospective Register of Systematic Reviews (PROSPERO database registration number: CRD42020154844).
Type of studies and participants
Both clinical trials and observational studies (including cross sectional, cohort and case–control studies) will be included. P. falciparum with confirmed chloroquine resistant or susceptible molecular markers. Several markers associated with P. falciparum antimalarial drug resistance have been identified (16). These include encoding chloroquine (CQ) resistance transporter (pfcrt) and multidrug resistance transporter-1 (pfmdr-1) both located on the food vacuole of the parasite involved in CQ resistance (17). However, the CQ transporter pfcrt is a stronger predictor of CQ resistance than pfmdr1 (18). Single nucleotide polymorphisms of pfcrt (K76T) in field isolates correlate with a resistance phenotype in in vitro assays and are sensitive markers for treatment failure in patients (19,20). The single K76 is for susceptible allele, single 76T is a marker for resistant allele while K76/76T (susceptible/resistant) is for mixed alleles (13).
Types of interventions and outcomes
Countries with restricted use and/or withdrawal of CQ for treatment of malaria infection. Following withdrawal of CQ use as first line malaria treatment, studies have reported increasing number of CQ susceptible species in several countries with subsequent dropping of CQ resistance (4,13,14,21). Invitro prevalence of chloroquine resistant P. falciparum and/ or prevalence of chloroquine sensitive P. falciparum using pfcrt and pfmdr1 molecular markers.
We will systematically search PubMed/MEDLINE, EMBASE, COCHRANE central, Google Scholar and Web of science. We will consult thesis repositories to identify additional studies and search the websites of key healthcare organizations (WHO, public health agencies). Similarly, a grey literature search will be done with help of Google. Data from 2000 and onwards published in English will be included and searches will be re-run prior to the final analysis.
URL to search strategy
We will develop a rigorous systematic search strategy with a health sciences librarian who has systematic review experience using published guidelines of the Cochrane Collaboration. The strategy will be developed for PubMed/MEDLINE (Additional File 2) and EMBASE using keywords and MeSH (MEDLINE) or EMTREE (EMBASE). To be as inclusive as possible, we will limit the search strategy to terms covering the susceptible OR chloroquine resistant P. falciparum. Keywords such as pfcrt, pfmdr1, chloroquine, resistant, susceptible and P. falciparum will be used. This search strategy will also be adapted to the other databases.
Data extraction (selection and coding)
Study selection: Study selection will be managed using Covidence software (Australia) where two independent reviewers will evaluate articles for potential inclusion by screening titles and abstracts and will assess full publications to determine eligibility for final inclusion. Between each assessment, results will be discussed to reach a consensus on the interpretation of inclusion criteria. Any further disagreement on study eligibility will be resolved by consensus, and a third reviewer will be consulted if necessary. If information on eligibility is unavailable and/ or unclear, study authors will be contacted to clarify. Duplicate publications will be identified and removed using reference manager (Endnote X9, USA). Identified publication(s) will be analyzed using criteria based on most recent dates, largest sample size, maximum correspondence with inclusion criteria and minimal risk of bias.
Data coding: Data that will be extracted from study documents, including information about study design and methodology, participant demographics and baseline characteristics, prevalence of chloroquine resistant/ susceptible etc (Additional File 3). Unavailable, unclear information and/or additional details will be requested from the study investigators. Data will be recorded using excel spreadsheet and Systematic Review Data Repository-Plus.
Risk of bias (quality) assessment
Risk of bias in observational studies will be evaluated using the ROBINS-I risk of bias assessment tool for non-randomized studies. The tool evaluates baseline and time-varying confounding, co-interventions, selection bias, classification bias (intervention), missing data, and bias in outcome measurement. While for randomized controlled trials risk of bias will be evaluated using the Cochrane risk of bias tool. Two reviewers will independently evaluate risk of bias and rate studies using respective tools (low, moderate serious, critical, unclear for the ROBINS-I tool and high, low, unclear for the Cochrane risk of bias tool). Disagreement will be resolved using arbitration by a third reviewer
Strategy for data synthesis
Depending on data availability the trend of chloroquine resistance will be sorted per year based on change of chloroquine treatment. For heterogeneity across studies in terms of populations, design, methods, intervention, and/or outcome (s) will be presented using a systematic narrative synthesis. We will explore the results according to categories of interventions and outcomes taking account of risk of bias, in line with Centre for Reviews and Dissemination recommendations. The narrative will be written by the lead reviewer and then checked independently by at least one other reviewer. A third reviewer will adjudicate any disagreements. We will measure heterogeneity for each meta-analysis using I2.
Analysis of subgroups or subsets
When data available the trend of chloroquine resistance will be sorted based on year of abandonment in every country.