{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,20]],"date-time":"2026-08-20T21:25:28Z","timestamp":1787261128483,"version":"build-2736575974"},"reference-count":21,"publisher":"Oxford University Press (OUP)","issue":"5","license":[{"start":{"date-parts":[[2026,8,4]],"date-time":"2026-08-04T00:00:00Z","timestamp":1785801600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/academic.oup.com\/pages\/standard-publication-reuse-rights"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[2026,8,4]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                  <jats:sec>\n                    <jats:title>Introduction<\/jats:title>\n                    <jats:p>Hemoglobin A1c has a stringent total allowable error (TEa), making high Six Sigma values difficult to attain. In addition, data from ambulatory accredited laboratories are sparse.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>Internal quality control (QC) data for 2 levels were collected over 8 months on a single-lot Bio-Rad D-10 high-performance liquid chromatography analyzer. Long-term imprecision was the coefficient of variation (s\/x\u00af)\u2009\u00d7\u2009100 (CV) of all internal QC results combined, capturing between-month variation. Bias was derived from external quality assessment (EQAS) and assigned QC targets, applied as absolute values. The Sigma metric was (TEa\u2009\u2012\u2009absolute bias)\u2009\/\u2009CV at TEa levels of 6%, 7%, and 8%; the Quality Goal Index distinguished imprecision-driven from bias-driven performance.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>Long-term CVs were 3.04% (level 1) and 1.34% (level 2); EQASs were satisfactory throughout. At a TEa of 6% with EQAS-derived bias, Sigma metrics were 1.19 and 2.70 and, with a level-specific QC target bias, 1.46 and 4.22. At the Clinical Laboratory Improvement Amendments 2025 criterion of 8%, the Sigma metrics were 2.11 and 5.71. The level 1 Quality Goal Index (0.52) identified imprecision as predominant.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Discussion<\/jats:title>\n                    <jats:p>Despite satisfactory external proficiency, Sigma metrics fell below 3 at both levels against a 6% TEa and below 2 at the clinically pivotal lower concentration, driven by imprecision rather than bias. No control strategy compensates for this; therefore, we proposed a precision-focused corrective plan that targets between-month instability.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1093\/labmed\/lmag052","type":"journal-article","created":{"date-parts":[[2026,8,5]],"date-time":"2026-08-05T11:48:40Z","timestamp":1785930520000},"source":"Crossref","is-referenced-by-count":0,"title":["Sigma metric and Quality Goal Index assessment of hemoglobin A1c analytical performance in an ambulatory accredited laboratory"],"prefix":"10.1093","volume":"57","author":[{"ORCID":"https:\/\/orcid.org\/0009-0002-8796-6432","authenticated-orcid":false,"given":"Jagdish","family":"Chandarana","sequence":"first","affiliation":[{"name":"Vedant Diagnostic Center , Rajkot, Gujarat,","place":["India"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0007-7861-3068","authenticated-orcid":false,"given":"Kinjal","family":"Butani","sequence":"additional","affiliation":[{"name":"Department of Laboratory Medicine, Vedant Diagnostic Center , Rajkot, Gujarat,","place":["India"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"286","published-online":{"date-parts":[[2026,8,20]]},"reference":[{"key":"2026082016495161400_lmag052-B1","volume-title":"Six Sigma Quality Design and Control: Desirable Precision and Requisite QC for Laboratory Measurement Processes","author":"Westgard","year":"2006","edition":"2nd"},{"key":"2026082016495161400_lmag052-B2","doi-asserted-by":"publisher","first-page":"1629","DOI":"10.1093\/clinchem\/36.9.1629","article-title":"Precision requirements for cost-effective operation of analytical processes","volume":"36","author":"Westgard","year":"1990","journal-title":"Clin Chem"},{"key":"2026082016495161400_lmag052-B3","doi-asserted-by":"publisher","first-page":"020502","DOI":"10.11613\/BM.2018.020502","article-title":"Analytical Sigma metrics: a review of Six Sigma implementation tools for medical laboratories","volume":"28","author":"Westgard","year":"2018","journal-title":"Biochem Med (Zagreb)"},{"key":"2026082016495161400_lmag052-B4","doi-asserted-by":"publisher","first-page":"581","DOI":"10.1373\/jalm.2016.022269","article-title":"What\u2019s new in laboratory statistical quality control guidance? 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