Gizem Yılmaz Çalık

Background/Objectives: Reference intervals (RIs) for thyroid-stimulating hormone (TSH), free thyroxine (FT4), and free triiodothyronine (FT3) are essential for accurate interpretation of thyroid function tests. Given the pronounced age- and sex-related biological variability of these analytes, locally derived and population-specific RIs are required. Methods: This multicenter study estimated age- and sex-specific RIs for TSH, FT4, and FT3 using an indirect statistical approach applied to routine laboratory information system data from three hospitals in Ankara, Türkiye. Measurements were performed on Maglumi X8 and X6 analyzers (Snibe Diagnostic, Shenzhen, China) using chemiluminescent immunoassays. Reference intervals were calculated using the refineR algorithm implemented in the R programming language, with Box–Cox or shifted two-parameter (mod) Box–Cox transformations selected according to data distribution. Results: More than 100,000 test results were included after predefined exclusions. In adults (≥18 years), the estimated TSH reference intervals were 0.495–5.83 mIU/L in males and 0.485–6.40 mIU/L in females, with higher upper limits observed in females. Adult FT4 reference intervals were approximately 12.9–21.5 pmol/L, and FT3 intervals were 3.46–6.04 pmol/L in males and 3.46–5.76 pmol/L in females. Pediatric reference intervals for TSH and FT4 were also derived across predefined age categories, demonstrating age-dependent variation. Conclusions: This study establishes age- and sex-stratified reference intervals for TSH, FT4, and FT3 using large multicenter routine laboratory datasets, encompassing both adult and pediatric populations. The findings highlight limitations of manufacturer-provided intervals and support the application of indirect statistical approaches, such as refineR, for local reference interval determination in clinical laboratories.

Objectives Urine samples are frequently used in the clinical practice. In our study, we aimed to calculate the biological variations (BV) of analytes and analyte/creatinine ratios measured in spot urine. Methods Second-morning spot urine samples were collected from 33 (16 female, 17 male) healthy volunteers once weekly for 10 weeks and analyzed in the Roche Cobas 6,000 instrument. Statistical analyzes were performed using BioVar, an online BV calculation software. The data were evaluated in terms of normality, outliers, steady state, homogeneity of the data, and BV values were obtained by analysis of variance (ANOVA). A strict protocol was established for within-subject (CV_I) and between-subject (CV_G) estimates for both genders. Results There was a significant difference between female/male CV_I estimates of all analytes except potassium, calcium and magnesium. No difference was found in CV_G estimates. When the analytes that had a significant difference in CV_I estimates in spot urine analytes were compared to creatinine, it was observed that the significant difference between the genders disappeared. There was no significant difference between female/male CV_I and CV_G estimates in all spot urine analyte/creatinine ratios. Conclusions Since the CV_I estimates of analyte/creatinine ratios are lower, it would be more reasonable to use them in result reporting. Reference ranges should be used with caution, since II values of almost all parameters are between 0.6 and 1.4. The CV_I detection power of our study is 1, which is the highest value.

Aim: Diagnostic biomarkers are needed for pediatric acute appendicitis (AA). We hypothesized that presepsin (soluble CD14 subtype), a biomarker for sepsis, can also be used in pediatric AA and aimed to investigate its diagnostic value in those patients. Materials and Methods: This prospective case-control study was conducted on children admitted to the Pediatric Emergency Department with suspected acute appendicitis. Serum levels of interleukin-6, and presepsin were statistically analyzed for their diagnostic values. Results: No remarkable demographic differences were present between the 41 cases and 47 controls. Clinical and routine laboratory findings were significantly positive for acute appendicitis in the cases compared to controls. ROC analysis indicated an AUC for presepsin as 0.999 (CI 95%: 0.890-0.993) and for interleukin-6 as 0.963 (CI 95%:0.949-1.000). The best cut-off point value for presepsin was at 739 pg/ml, corresponding to a sensitivity of 97.56% and a specificity of 100%. The best cut-off point value for interleukin-6 was at 19 pg/ml, corresponding to a sensitivity of 97.56% and a specificity of 90.32%. Conclusions: Our study results indicate that presepsin can be considered a biomarker for diagnosing appendicitis in pediatric cases. Future studies might better include the combination with other biomarkers in pediatric cases.