Search strategy: The PubMed, Embase, and Cochrane library databases were searched. All articles on the prevalence of hyperuricemia in adolescents published from Jan 1, 2000 to Dec 10, 2019 were searched comprehensively using the keywords “Adolescents”, “Adolescence”, “Teens”, “Teen”, “Teenagers”, “Teenager”, “Youth”, “Youths”, “Adolescents, Female”, “Adolescent, Female”, “Female Adolescent” or “Female Adolescents”, “Adolescents, Male” or “Adolescent, Male”, “Male Adolescent” or “Male Adolescents”, “Infant” “Infants”, “Child, Preschool'', “Preschool Child”, “Children, Preschool”, “Preschool Children”, “Child”, “Children”, “Hyperuricemia”, “asymptomatic hyperuricemia”, “HUA”, “HU”, “uric acid”, “Prevalence”, “Incidence”, “Epidemiology”, “Prevalences” , and “Incidences”.
Inclusion and Exclusion Criteria: Papers were included if they met all of the following criteria: (1) all study participants were adolescents; (2) study data were general (i.e., population- rather than hospital-based); (3) original research; (4) clearly stated study date; and (5) the most detailed study among duplicate studies of the same population (where applicable).
Studies were excluded if they (1) were not original research, such as a review or case report, (2) included participants with concomitant diseases or a history of taking medications known to affect uric acid metabolism, (3) were animal studies or (4) cohort studies, or (5) had a small sample size.
Definitions of Hyperuricemia and Gout: The diagnostic criteria used for hyperuricemia for adolescents varied among the studies; we have listed the criteria in Table 1.
Data extraction: Two researchers screened the literature independently and the screening results were cross-checked. For studies where suitability for inclusion was difficult to determine, group discussions were held to reach a consensus. According to the pre-designed data extraction table, the data were extracted independently, and the extraction results were cross-checked. The extracted data included the first author, study year, country, publication year, sample size, number of cases, and age of onset. We used the framework proposed by the Cochrane Partnership to assess the quality of the research. Study quality was assessed independently by three reviewers. If two or three reviewers were in agreement, the study was included in the meta-analysis. All data included in the study were tabulated and bias was determined during the quality-assessment phase.
Data analysis: The statistical analyses were performed using STATA software (ver. 15.0; StataCorp., College Station, TX, USA). First, a heterogeneity test was performed on the included studies. The heterogeneity statistic, I2, was classified as follows: 25%, low heterogeneity; 50%, high heterogeneity; and 75%, high heterogeneity. If the heterogeneity among the included studies was low (I2 ≤ 50%, P > 0.05), a fixed effect model was used; when there was high heterogeneity among the included studies (I2 > 50%, P < 0.05), a random effect model was adopted. Subgroup analyses were also performed according to gender, age, and region.