{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,24]],"date-time":"2026-09-24T05:45:21Z","timestamp":1790228721528,"version":"4.1.0"},"reference-count":13,"publisher":"Walter de Gruyter GmbH","issue":"1","license":[{"start":{"date-parts":[[2025,9,3]],"date-time":"2025-09-03T00:00:00Z","timestamp":1756857600000},"content-version":"unspecified","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0"}],"funder":[{"DOI":"10.13039\/501100004587","name":"Instituto de Salud Carlos III","doi-asserted-by":"publisher","award":["PI20\/00922"],"award-info":[{"award-number":["PI20\/00922"]}],"id":[{"id":"10.13039\/501100004587","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100004587","name":"Instituto de Salud Carlos III","doi-asserted-by":"publisher","award":["PI23\/0174"],"award-info":[{"award-number":["PI23\/0174"]}],"id":[{"id":"10.13039\/501100004587","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[2026,3,16]]},"abstract":"Abstract<\/jats:title>\n \n Objectives<\/jats:title>\n \n Urinary acidification plays a crucial role in acid-base homeostasis, its evaluation being necessary in the differential diagnosis of metabolic acidosis. The practical limitations of the functional tests required to confirm an acidification disorder point out the need for a simple screening method for urinary acidification assessment in spot urine. The best candidates are urine pH\u00a0and ammonium (NH\n 4<\/jats:sub>\n +<\/jats:sup>\n ), but there are few data on their reference values in spot urine in children.\n <\/jats:p>\n <\/jats:sec>\n \n Methods<\/jats:title>\n \n Our study measured urine pH\u00a0and NH\n 4<\/jats:sub>\n +<\/jats:sup>\n \/creatinine ratio in the first morning fasting urine of 135 healthy children aged between 5 and 14\u00a0years. pH\u00a0was measured by dipstick and potentiometry, concluding that only potentiometric measures were appropriated for assessing urinary acidification in acid-base diseases.\n <\/jats:p>\n <\/jats:sec>\n \n Results<\/jats:title>\n \n Median urine pH\u00a0was 5.67 (interquartile range 5.44\u20136.01), ranging from 4.90 to 7.60. Median NH\n 4<\/jats:sub>\n +<\/jats:sup>\n \/creatinine ratio was 4,869\u202f\u03bcmol\/mmol (interquartile range 3,528\u20135,918). The reference interval for urine pH\u00a0ranged from 5.01 to 6.88 and the reference interval for NH\n 4<\/jats:sub>\n +<\/jats:sup>\n \/creatinine ratio ranged from 1,646\u202f\u03bcmol\/mmol to 9,799\u202f\u03bcmol\/mmol.\n <\/jats:p>\n <\/jats:sec>\n \n Conclusions<\/jats:title>\n These results supply, for the first time, paediatric reference values for both parameters simultaneously, standardizing the sample and method of choice and providing a clinically useful tool for a preliminary evaluation of urinary acidification.<\/jats:p>\n <\/jats:sec>","DOI":"10.1515\/almed-2025-0070","type":"journal-article","created":{"date-parts":[[2025,9,3]],"date-time":"2025-09-03T06:56:12Z","timestamp":1756882572000},"page":"64-67","source":"Crossref","is-referenced-by-count":1,"title":["Urine pH\u00a0and ammonium paediatric reference intervals in first morning spot urine"],"prefix":"10.1515","volume":"7","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-8362-2387","authenticated-orcid":false,"given":"Lucas Ram\u00f3n","family":"D\u00edaz-Anad\u00f3n","sequence":"first","affiliation":[{"name":"Department of Childhood and Adolescence , 16474 Hospital Universitario Central de Asturias , Oviedo , Spain"},{"name":"Department of Medicine , Universidad de Oviedo , Spain"},{"name":"Department of Paediatrics , Hospital Carmen y Severo Ochoa , Cangas del Narcea , Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4621-8905","authenticated-orcid":false,"given":"Juli\u00e1n","family":"Rodr\u00edguez","sequence":"additional","affiliation":[{"name":"Department of Childhood and Adolescence , 16474 Hospital Universitario Central de Asturias , Oviedo , Spain"},{"name":"Department of Medicine , Universidad de Oviedo , Spain"},{"name":"Paediatric Research Group , Instituto de Investigaci\u00f3n Sanitaria del Principado de Asturias (ISPA) , Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5003-9195","authenticated-orcid":false,"given":"Flor \u00c1ngel","family":"Ord\u00f3\u00f1ez-\u00c1lvarez","sequence":"additional","affiliation":[{"name":"Department of Childhood and Adolescence , 16474 Hospital Universitario Central de Asturias , Oviedo , Spain"},{"name":"Paediatric Research Group , Instituto de Investigaci\u00f3n Sanitaria del Principado de Asturias (ISPA) , Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8790-1391","authenticated-orcid":false,"given":"Helena","family":"Gil-Pe\u00f1a","sequence":"additional","affiliation":[{"name":"Department of Childhood and Adolescence , 16474 Hospital Universitario Central de Asturias , Oviedo , Spain"},{"name":"Department of Medicine , Universidad de Oviedo , Spain"},{"name":"Paediatric Research Group , Instituto de Investigaci\u00f3n Sanitaria del Principado de Asturias (ISPA) , Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"\u00d3scar David","family":"Pons-Belda","sequence":"additional","affiliation":[{"name":"Department of Clinical Analysis , Hospital Can Misses , Eivissa , Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5204-713X","authenticated-orcid":false,"given":"Leire","family":"Cardo","sequence":"additional","affiliation":[{"name":"Department of Clinical Biochemistry, Laboratory Medicine , 16474 Hospital Universitario Central de Asturias , Oviedo , Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"374","published-online":{"date-parts":[[2025,9,3]]},"reference":[{"key":"2026031722063444275_j_almed-2025-0070_ref_001","doi-asserted-by":"crossref","unstructured":"Santos, F, Ord\u00f3\u00f1ez, FA, Claramunt-Taberner, D, Gil-Pe\u00f1a, H. Clinical and laboratory approaches in the diagnosis of renal tubular acidosis. Pediatr Nephrol 2015;30:2099\u2013107. https:\/\/doi.org\/10.1007\/s00467-015-3083-9.","DOI":"10.1007\/s00467-015-3083-9"},{"key":"2026031722063444275_j_almed-2025-0070_ref_002","doi-asserted-by":"crossref","unstructured":"Trepiccione, F, Walsh, SB, Ariceta, G, Boyer, O, Emma, F, Camilla, R, et al.. Distal renal tubular acidosis: ERKNet\/ESPN clinical practice points. Nephrol Dial Transplant. 2021;36:1585\u201396. https:\/\/doi.org\/10.1093\/ndt\/gfab171.","DOI":"10.1093\/ndt\/gfab171"},{"key":"2026031722063444275_j_almed-2025-0070_ref_003","doi-asserted-by":"crossref","unstructured":"Carlisle, EJ, Donnelly, SM, Halperin, ML. Renal tubular acidosis (RTA): recognize the ammonium defect and pHorget the urine pH. Pediatr Nephrol 1991;5:242\u20138. https:\/\/doi.org\/10.1007\/bf01095965.","DOI":"10.1007\/BF01095965"},{"key":"2026031722063444275_j_almed-2025-0070_ref_004","doi-asserted-by":"crossref","unstructured":"Bilobrov, VM, Chugaj, AV, Bessarabov, VI. Urine pH\u00a0variation dynamics in healthy individuals and stone formers. Urol Int. 1990;45:326\u201331. https:\/\/doi.org\/10.1159\/000281730.","DOI":"10.1159\/000281730"},{"key":"2026031722063444275_j_almed-2025-0070_ref_005","doi-asserted-by":"crossref","unstructured":"Skinner, R, Cole, M, Pearson, ADJ, Coulthard, MG, Craft, AW. Specificity of pH\u00a0and osmolality of early morning urine sample in assessing distal renal tubular function in children: results in healthy children. BMJ 1996;312:1337\u20138. https:\/\/doi.org\/10.1136\/bmj.312.7042.1337.","DOI":"10.1136\/bmj.312.7042.1337"},{"key":"2026031722063444275_j_almed-2025-0070_ref_006","unstructured":"Chafe, L, Gault, MH. First morning urine pH\u00a0in the diagnosis of renal tubular acidosis with nephrolithiasis. Clin Nephrol. 1994;41:159\u201362."},{"key":"2026031722063444275_j_almed-2025-0070_ref_007","doi-asserted-by":"crossref","unstructured":"Cunarro, JA, Weiner, MW. A comparison of methods for measuring urinary ammonium. Kidney Int. 1974;5:303\u20135. https:\/\/doi.org\/10.1038\/ki.1974.41.","DOI":"10.1038\/ki.1974.41"},{"key":"2026031722063444275_j_almed-2025-0070_ref_008","doi-asserted-by":"crossref","unstructured":"Ha, LY, Chiu, WW, Davidson, JS. Direct urine ammonium measurement: time to discard urine anion and osmolar gaps. Ann Clin Biochem 2012;49:606\u20138. https:\/\/doi.org\/10.1258\/acb.2012.012013.","DOI":"10.1258\/acb.2012.012013"},{"key":"2026031722063444275_j_almed-2025-0070_ref_009","doi-asserted-by":"crossref","unstructured":"Gruzdys, V, Cahoon, K, Pearson, L, Raphael, KL. Measurement of urinary ammonium using a commercially available plasma ammonium assay. Kidney360 2022;3:926\u201332. https:\/\/doi.org\/10.34067\/kid.0000262022.","DOI":"10.34067\/KID.0000262022"},{"key":"2026031722063444275_j_almed-2025-0070_ref_010","doi-asserted-by":"crossref","unstructured":"Uribarri, J, Goldfarb, DS, Raphael, KL, Rein, JL, Asplin, JR. Beyond the urine anion gap: in support of the direct measurement of urinary ammonium. A Am J Kidney Dis 2022;80:667\u201376. https:\/\/doi.org\/10.1053\/j.ajkd.2022.05.009.","DOI":"10.1053\/j.ajkd.2022.05.009"},{"key":"2026031722063444275_j_almed-2025-0070_ref_011","unstructured":"Clinical and Laboratory Standards Institute (CLSI). Defining, establishing, and verifying reference intervals in the clinical laboratory; approved Guideline\u20143rd ed. CLSI document EP28-A3c. Wayne, PA: CLSI; 2008."},{"key":"2026031722063444275_j_almed-2025-0070_ref_012","doi-asserted-by":"crossref","unstructured":"Cardo, L, Gil-Pe\u00f1a, H, Garc\u00eda-Garc\u00eda, M, Fern\u00e1ndez, JC, Santos, F, \u00c1lvarez, FV. Implementation of an automated method for direct quantification of urinary ammonium. Clin Chem Lab Med CCLM 2019;57:203\u20135.","DOI":"10.1515\/cclm-2018-1250"},{"key":"2026031722063444275_j_almed-2025-0070_ref_013","doi-asserted-by":"crossref","unstructured":"Cardo, L, Gil-Pe\u00f1a, H, \u00c1lvarez, FV, Santos, F. Urinary ammonium: paediatric reference values. Acta Paediatr 2021;110:659\u201360. https:\/\/doi.org\/10.1111\/apa.15544.","DOI":"10.1111\/apa.15544"}],"container-title":["Advances in Laboratory Medicine \/ Avances en Medicina de Laboratorio"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.degruyterbrill.com\/document\/doi\/10.1515\/almed-2025-0070\/xml","content-type":"application\/xml","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/www.degruyterbrill.com\/document\/doi\/10.1515\/almed-2025-0070\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,3,17]],"date-time":"2026-03-17T22:06:40Z","timestamp":1773785200000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.degruyterbrill.com\/document\/doi\/10.1515\/almed-2025-0070\/html"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2025,9,3]]},"references-count":13,"journal-issue":{"issue":"1","published-online":{"date-parts":[[2025,9,3]]},"published-print":{"date-parts":[[2026,3,16]]}},"alternative-id":["10.1515\/almed-2025-0070"],"URL":"https:\/\/doi.org\/10.1515\/almed-2025-0070","relation":{},"ISSN":["2628-491X"],"issn-type":[{"value":"2628-491X","type":"electronic"}],"subject":[],"published":{"date-parts":[[2025,9,3]]}}}