To assess available evidence on global patterns of STH reinfection after drug treatment.
To identify the frequency and leading determinants of STH reinfection through pooled risk estimates.
We aimed to include all published studies in English or Chinese in which reinfection with STH was measured, for the period 1 January 1923 to 31 December 2010. Both observational studies and trials were eligible for inclusion.
We identified published studies using the Web of Science, EMBASE, China National Knowledge Infrastructure (CNKI), WanFang Database, and Chinese Scientific Journal Database.
Types of study to be included
Both observational studies and trials were eligible for inclusion. We excluded the following studies:
(i) data without rate of infection after preventive chemotherapy;
(ii) where time of follow-up was less than 2 months or more than 3 years;
(iii) hospital-based or case studies in which the representativeness of the sample for the general population was unknown;
(iv) duplicate publication or extended analysis of previously published studies.
Condition or domain being studied
Soil-transmitted helminth (STH) infections (i.e., Ascaris lumbricoides, hookworm, and Trichuris trichiura) are still highly endemic in developing countries. Preventive chemotherapy through mass drug administration is the mainstay of control but is challenged by rapid reinfection.
Any population except that in hospital-based or case studies in which the representativeness of the sample for the general population was unknown.
Preventive chemotherapy to control STH infection.
1) Rate and intensity of infection before treatment were extracted to compare with that after treatment.
2) Subgroups with different socioecnomic characteristics or factors such as initial infection (present or absent), initial infection intensity (light or heavy), age, sex, nutrient supplementation, health promotion, geophagy, education or occupation of mother, crowded housing, type of floor or yard, sanitary latrine, and so on.
Reinfection rate at 3, 6, and 12 months posttreatment, expressed by prevalence risk ratio (PRR=prevalence after treatment/prevalence before treatment).
Determinants of predisposition to STHs reinfection, assessed by risk ratios (RR).
Data extraction, (selection and coding)
Only one reviewer (TWJ) extracts data followed by a second reviewer (SM) going through the extracted data according to inclusion and exclusion criteria. We abstract and compare the following components associated with STH reinfection: rate and intensity of infection before and after treatment, CR, time between evaluations before and after treatment, and adherence to follow-up. Additional study characteristics included year and country where the trial was implemented, sample size, age of study participants, diagnostic method, and strategy of drug administration (universal, targeted, or selective treatment).
Risk of bias (quality) assessment
Pooled estimates are calculated by a random-effect model unless heterogeneity level determined by I-squared was no more than 50%. Publication bias is visually examined using funnel plots.
Adherence and cure rate are used to assess the quality of individual studies. A low adherence rate could create outliers with a large effect on the pooled estimate, while a low CR could directly limit effective measurement of reinfection rates within 6 months after drug administration. We therefore remove such cohorts from our final pooled estimates.
Strategy for data synthesis
Review Manager Software 5.0.23, provided by the Cochrane Collaboration group, is used for meta-analysis. For dichotomous data, risk ratios (RR) are listed by study and compared for the risk or predisposition to reinfection after preventive chemotherapy. The primary analysis is performed according to helminth species-specific infection and length of follow-up intervals. Additional analysis is performed for specific population subgroups. Besides the above, a brief narrative synthesis is used to summarize some important outcomes which cannot be pooled due to the broad differences in the measures and statistical methods.
Analysis of subgroups or subsets
Subgroup analysis is based on initial infection status, age, sex, and selected socioeconomic factors.
Contact details for further information
Organisational affiliation of the review
National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention, People’s Republic of China
Dr Tie-Wu Jia, National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention, People’s Republic of China Dr Sara Melville, Hughes Hall College, Cambridge University, United Kingdom Dr Jürg Utzinger, Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute and University of Basel, Basel, Switzerland Dr Charles H King, Center for Global Health and Diseases, Case Western Reserve University School of Medicine, Cleveland, Ohio, United States of America Dr Xiao-Nong Zhou, National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention, People’s Republic of China
Miss Helen Wakeford, Hughes Hall College, Cambridge University, United Kingdom Mr Paul Chinnock, Hughes Hall College, Cambridge University, United Kingdom Professor Long-Qi Xu, National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention, People’s Republic of China Professor Ming-Gang Chen, National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention, People’s Republic of China Mr Wei Li, Jiangsu Institute of Parasitic Diseases, People’s Republic of China
Details of any existing review of the same topic by the same authors
Anticipated or actual start date
08 February 2011
Anticipated completion date
30 November 2011
Dr Jia gratefully acknowledges TDR/TropIKA.net for a Career Development Fellowship (CDF).
Formal screening of search results against eligibility criteria
Risk of bias (quality) assessment
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