Review Papers Claim by Claim

Concise critical appraisal (visual → text)

1. Data summarized: The review screened 285 records, included 46 papers (28 seroprevalence studies), and reports general-population IgG between 0–12.4% and much higher prevalence in certain risk-groups; these core results are taken directly from the paper Leblebicioglu & Ozaras 2018 (systematic review)
2. Strength — structured review & PRISMA: The authors adhered to PRISMA guidance and used three major databases, which is appropriate for a descriptive epidemiologic synthesis PRISMA statement (Liberati et al.)
3. Key methodological limitations (why reported prevalences are uncertain):
   • Geographic and sampling bias: most primary studies are from Ankara, Istanbul and a few provinces — not a representative national sampling frame; authors acknowledge this Leblebicioglu & Ozaras 2018 (geographic bias)
   • Heterogeneous assays: anti-HEV IgG assay performance strongly affects seroprevalence estimates (variable sensitivity/specificity between ELISAs) — this is a major source of measurement bias and was highlighted by the authors and independent assay-evaluation papers Wenzel et al. 2013 (assay variability)
   • Small sample sizes / convenience samples: many constituent studies are underpowered to estimate regional prevalence or identify risk factors; the review repeatedly flags this (limits meta-analysis possibilities) Leblebicioglu & Ozaras 2018 (sample size limits)
4. Interpretation cautions: High prevalence in specific groups (e.g., 54% in chronic HCV patients reported from one study) may reflect shared exposure routes, selection bias (referral/clinic populations), or assay differences; single-study extremes should not be generalized without multicenter confirmation Bayram et al. 2007 (CHB/CHC seroprevalence)
5. Gaps & blindspots (authors + additional):
   • Little or no data on immunosuppressed / solid-organ transplant recipients despite clinical importance (review notes absence) Leblebicioglu & Ozaras 2018 (immunosuppressed gap)
   • Environmental and zoonotic surveillance sparse (no systematic national water/food/animal surveillance data were found), limiting conclusions about transmission pathways; a 1998 doctoral thesis found HEV-RNA in 3/150 diverse water samples — preliminary and not nationally representative Leblebicioglu & Ozaras 2018 (environmental data missing)
   • Temporal heterogeneity: included studies span decades (1990s–2015), during which assay technology and exposures changed; combining old and new seroprevalences without assay-standardization risks biased trends.
6. Practical conclusion: The review is a careful descriptive aggregation and useful map of existing Turkish HEV literature (useful baseline). However, the central epidemiological claims (endemicity, population burden) remain provisional because of non-representative sampling and assay heterogeneity; the authors' call for standardized, multicenter sero-surveys and inclusion of immunosuppressed/transplant populations is well-justified Leblebicioglu & Ozaras 2018 (conclusion & recommendation)

Where the evidence would change the conclusion (falsification test)

A large, prospectively sampled, multi-region Turkish serosurvey (representative sampling frame), using a single high-performance validated anti-HEV IgG assay (and HEV RNA testing in suspects), showing consistently low seroprevalence across regions and risk groups would falsify the claim that Turkey is generally HEV-endemic; conversely, standardized high rates would strengthen endemicity claims. The review itself lists this as the crucial missing test Leblebicioglu & Ozaras 2018 (need for definitive studies)

Actionable recommendations for next studies (brief)

• Design a nationally representative cross-sectional serosurvey sampling all 7 geographical regions with stratification by rural/urban, age, and key occupations; power sample sizes to estimate regional prevalence within ±2–3% precision.
• Use a single validated high-sensitivity/high-specificity IgG assay (and confirm borderline positives by neutralization/Western blot or orthogonal assay) to reduce measurement heterogeneity Wenzel et al. 2013 (assay selection).
• Include immunosuppressed/transplant cohorts and parallel environmental (water/food/pig/animal) surveillance with RT-PCR and sequencing to map genotypes and probable transmission routes.

Confidence note: The systematic review correctly compiles published Turkish HEV data up to mid-2017; confidence in the review’s descriptive mapping is moderate, but confidence in extrapolating a national endemicity claim is low until standardized, representative data are produced. Primary reasons: geographic sampling bias, assay heterogeneity, and small study sizes Leblebicioglu & Ozaras 2018 (confidence caveat)