{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,28]],"date-time":"2026-08-28T19:17:51Z","timestamp":1787944671562,"version":"build-2784847793"},"reference-count":28,"publisher":"MDPI AG","issue":"17","license":[{"start":{"date-parts":[[2026,8,28]],"date-time":"2026-08-28T00:00:00Z","timestamp":1787875200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Diagnostics"],"abstract":"<jats:p>Background\/Objectives: Interpretation of amino-acid and acylcarnitine results in newborn screening depends on population-appropriate reference intervals (RIs), and no locally derived paediatric RIs have been published for the general Kazakhstan population. We aimed to establish the first age- and sex-specific RIs for a tandem mass spectrometry (MS\/MS) panel measured from dried blood spots (DBSs) by flow injection analysis tandem mass spectrometry (FIA-MS\/MS) in a Kazakhstani paediatric population using an indirect (data-mining) approach. Methods: All amino-acid and acylcarnitine results (1 January 2022 to the data freeze on 20 July 2026) were extracted from the consolidated laboratory information system of a 21-branch network; after cleaning, deduplication and selection of conditionally healthy subjects, RIs (2.5th, 50th, 97.5th percentiles with 90% bootstrap confidence intervals) were computed per CLSI EP28-A3c across CALIPER age strata, with the neonatal period split into 0\u20137\/8\u201314\/15\u201328-day strata, and cross-validated by the canonical refineR package run without flag-based selection, the CLIR\/Mayo database and a comparable Turkish study. Results: From 687,726 results in 4198 patients, the conditionally healthy cohort comprised 3589 subjects; the large majority of analyte\u2013age strata permitted full CLSI EP28 computation. Canonical refineR and flag-based estimates agreed within \u00b130% in 91% of key-marker limits (median relative difference 9.6%), indicating that flag-based selection did not materially bias the upper limits. Reference intervals are reported for all amino acids and all 36 acylcarnitines of the panel. The valine 97.5th-percentile upper limit exceeded its 250 \u00b5mol\/L decision limit at 0\u201328 days (275.3 \u00b5mol\/L). Conclusions: We provide locally derived and internally cross-checked paediatric MS\/MS RIs, pending prospective verification, and flag two actionable findings: inter-site harmonisation of several key markers and the overlap of the upper-normal valine limit with its clinical decision limit.<\/jats:p>","DOI":"10.3390\/diagnostics16172766","type":"journal-article","created":{"date-parts":[[2026,8,28]],"date-time":"2026-08-28T18:33:52Z","timestamp":1787942032000},"page":"2766","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Age- and Sex-Specific Reference Intervals for Amino Acids and Acylcarnitines by Tandem Mass Spectrometry in a Kazakhstani Paediatric Population: An Indirect Data-Mining Study"],"prefix":"10.3390","volume":"16","author":[{"given":"Yerlan","family":"Suleimenov","sequence":"first","affiliation":[{"name":"Head Office, CDL Olymp LLP (Laboratory Network), Astana 010000, Kazakhstan"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"supervision","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"},{"role":"formal-analysis","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8753-1802","authenticated-orcid":false,"given":"Ayat","family":"Assemov","sequence":"additional","affiliation":[{"name":"Head Office, CDL Olymp LLP (Laboratory Network), Astana 010000, Kazakhstan"},{"name":"School of Medicine, Nazarbayev University, Astana 010000, Kazakhstan"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"writing-original-draft","vocabulary":"credit"},{"role":"formal-analysis","vocabulary":"credit"},{"role":"validation","vocabulary":"credit"},{"role":"conceptualization","vocabulary":"credit"},{"role":"visualization","vocabulary":"credit"},{"role":"data-curation","vocabulary":"credit"},{"role":"software","vocabulary":"credit"},{"role":"methodology","vocabulary":"credit"}]},{"given":"Dana","family":"Rsaldina","sequence":"additional","affiliation":[{"name":"R&D Department, MYRZA-KHAN LLP, Astana 010000, Kazakhstan"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"conceptualization","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9334-9516","authenticated-orcid":false,"given":"Amir","family":"Baikatov","sequence":"additional","affiliation":[{"name":"Brain Institute, Farabi National University, Almaty 050040, Kazakhstan"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"writing-review-editing","vocabulary":"credit"},{"role":"software","vocabulary":"credit"}]},{"given":"Albina","family":"Omarova","sequence":"additional","affiliation":[{"name":"Head Office, CDL Olymp LLP (Laboratory Network), Astana 010000, Kazakhstan"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"writing-review-editing","vocabulary":"credit"}]},{"given":"Antonina","family":"Bespalko","sequence":"additional","affiliation":[{"name":"Head Office, CDL Olymp LLP (Laboratory Network), Astana 010000, Kazakhstan"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"supervision","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"},{"role":"investigation","vocabulary":"credit"}]}],"member":"1968","published-online":{"date-parts":[[2026,8,28]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1797","DOI":"10.1373\/clinchem.2003.022178","article-title":"Use of tandem mass spectrometry for multianalyte screening of dried blood specimens from newborns","volume":"49","author":"Chace","year":"2003","journal-title":"Clin. Chem."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"174","DOI":"10.1016\/j.jpba.2014.03.047","article-title":"Mass spectrometry in clinical chemistry: The case of newborn screening","volume":"101","year":"2014","journal-title":"J. Pharm. Biomed. Anal."},{"key":"ref_3","unstructured":"Clinical and Laboratory Standards Institute (2010). Defining, Establishing, and Verifying Reference Intervals in the Clinical Laboratory; Approved Guideline\u2014Third Edition (EP28-A3c), CLSI."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"20","DOI":"10.1515\/cclm-2018-0073","article-title":"IFCC Committee on Reference Intervals and Decision Limits Indirect methods for reference interval determination\u2014Review and recommendations","volume":"57","author":"Jones","year":"2019","journal-title":"Clin. Chem. Lab. Med."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"30","DOI":"10.1515\/cclm-2018-0059","article-title":"Verification of reference intervals in routine clinical laboratories: Practical challenges and recommendations","volume":"57","author":"Ozarda","year":"2019","journal-title":"Clin. Chem. Lab. Med."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"1893","DOI":"10.1515\/cclm-2016-0793","article-title":"Recommendation for the review of biological reference intervals in medical laboratories","volume":"54","author":"Henny","year":"2016","journal-title":"Clin. Chem. Lab. Med."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"854","DOI":"10.1373\/clinchem.2011.177741","article-title":"Closing the gaps in pediatric laboratory reference intervals: A CALIPER database of 40 biochemical markers","volume":"58","author":"Colantonio","year":"2012","journal-title":"Clin. Chem."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"358","DOI":"10.1080\/10408363.2017.1379945","article-title":"The Canadian laboratory initiative on pediatric reference intervals: A CALIPER white paper","volume":"54","author":"Adeli","year":"2017","journal-title":"Crit. Rev. Clin. Lab. Sci."},{"key":"ref_9","first-page":"43","article-title":"Pediatric reference intervals for biochemical markers: Gaps and challenges, recent national initiatives and future perspectives","volume":"28","author":"Tahmasebi","year":"2017","journal-title":"EJIFCC"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"1107","DOI":"10.1016\/j.cca.2012.03.005","article-title":"Reference interval computation: Which method (not) to choose?","volume":"413","author":"Pavlov","year":"2012","journal-title":"Clin. Chim. Acta"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"5","DOI":"10.11613\/BM.2016.001","article-title":"Reference intervals: Current status, recent developments and future considerations","volume":"26","author":"Ozarda","year":"2016","journal-title":"Biochem. Med."},{"key":"ref_12","doi-asserted-by":"crossref","unstructured":"Zharmakhanova, G., Kononets, V., Balmagambetova, S., Syrlybayeva, L., Nurbaulina, E., Zhussupova, Z., Sakhanova, S., Ayaganov, D., Kim, S., and Zhumalina, A. (2024). Selective screening for inborn errors of metabolism using tandem mass spectrometry in West Kazakhstan children: Study protocol. Front. Genet., 14.","DOI":"10.3389\/fgene.2023.1278750"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"030201","DOI":"10.11613\/BM.2018.030201","article-title":"Informed consent and ethics committee approval in laboratory medicine","volume":"28","author":"Borovecki","year":"2018","journal-title":"Biochem. Med."},{"key":"ref_14","unstructured":"Clinical and Laboratory Standards Institute (2021). Dried Blood Spot Specimen Collection for Newborn Screening (NBS01), CLSI."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"1615","DOI":"10.1373\/clinchem.2009.131300","article-title":"National Academy of Clinical Biochemistry laboratory medicine practice guidelines: Follow-up testing for metabolic disease identified by expanded newborn screening using tandem mass spectrometry; executive summary","volume":"55","author":"Dietzen","year":"2009","journal-title":"Clin. Chem."},{"key":"ref_16","unstructured":"Clinical and Laboratory Standards Institute (2014). Liquid Chromatography-Mass Spectrometry Methods; Approved Guideline (C62-A), CLSI."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"16023","DOI":"10.1038\/s41598-021-95301-2","article-title":"refineR: A novel algorithm for reference interval estimation from real-world data","volume":"11","author":"Ammer","year":"2021","journal-title":"Sci. Rep."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"230","DOI":"10.1097\/GIM.0b013e31820d5e67","article-title":"Clinical validation of cutoff target ranges in newborn screening of metabolic disorders by tandem mass spectrometry","volume":"13","author":"McHugh","year":"2011","journal-title":"Genet. Med."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"648","DOI":"10.1038\/gim.2012.2","article-title":"Enhanced interpretation of newborn screening results without analyte cutoff values","volume":"14","author":"Marquardt","year":"2012","journal-title":"Genet. Med."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"889","DOI":"10.1038\/gim.2014.62","article-title":"Postanalytical tools improve performance of newborn screening by tandem mass spectrometry","volume":"16","author":"Hall","year":"2014","journal-title":"Genet. Med."},{"key":"ref_21","first-page":"030704","article-title":"Establishment of age- and gender-specific reference intervals for amino acids and acylcarnitines by tandem mass spectrometry in Turkish paediatric population","volume":"33","author":"Madenci","year":"2023","journal-title":"Biochem. Med."},{"key":"ref_22","unstructured":"Cohen, J. (1988). Statistical Power Analysis for the Behavioral Sciences, Lawrence Erlbaum Associates. [2nd ed.]."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"133","DOI":"10.1016\/0009-8981(80)90074-1","article-title":"The distribution of amino acids between plasma and erythrocytes","volume":"100","author":"Hagenfeldt","year":"1980","journal-title":"Clin. Chim. Acta"},{"key":"ref_24","doi-asserted-by":"crossref","unstructured":"Dijkstra, A.M., de Blaauw, P., van Rijt, W.J., Renting, H., Maatman, R.G., van Spronsen, F.J., Maase, R.E., Schielen, P.C., Derks, T.G., and Heiner-Fokkema, M.R. (2023). Important lessons on long-term stability of amino acids in stored dried blood spots. Int. J. Neonatal Screen., 9.","DOI":"10.3390\/ijns9030034"},{"key":"ref_25","doi-asserted-by":"crossref","unstructured":"He, F., Yang, R., Huang, X., Tian, Y., Pei, X., Bohn, M.K., Zou, L., Wang, Y., Li, H., and Wang, T. (2021). Reference standards for newborn screening of metabolic disorders by tandem mass spectrometry: A nationwide study on millions of Chinese neonatal populations. Front. Mol. Biosci., 8.","DOI":"10.3389\/fmolb.2021.719866"},{"key":"ref_26","first-page":"99","article-title":"Indirect reference intervals: Harnessing the power of stored laboratory data","volume":"40","author":"Farrell","year":"2019","journal-title":"Clin. Biochem. Rev."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"193","DOI":"10.1016\/j.ymgme.2020.01.006","article-title":"Branched-chain \u03b1-ketoacid dehydrogenase deficiency (maple syrup urine disease): Treatment, biomarkers, and outcomes","volume":"129","author":"Strauss","year":"2020","journal-title":"Mol. Genet. Metab."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"1012","DOI":"10.1373\/clinchem.2015.243055","article-title":"Transference and validation of reference intervals","volume":"61","author":"Tate","year":"2015","journal-title":"Clin. Chem."}],"container-title":["Diagnostics"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2075-4418\/16\/17\/2766\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,8,28]],"date-time":"2026-08-28T18:44:06Z","timestamp":1787942646000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2075-4418\/16\/17\/2766"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,8,28]]},"references-count":28,"journal-issue":{"issue":"17","published-online":{"date-parts":[[2026,9]]}},"alternative-id":["diagnostics16172766"],"URL":"https:\/\/doi.org\/10.3390\/diagnostics16172766","relation":{},"ISSN":["2075-4418"],"issn-type":[{"value":"2075-4418","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,8,28]]}}}