{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,1]],"date-time":"2026-09-01T20:23:57Z","timestamp":1788294237483,"version":"build-2803163510"},"reference-count":42,"publisher":"Wiley","issue":"3","license":[{"start":{"date-parts":[[2025,8,17]],"date-time":"2025-08-17T00:00:00Z","timestamp":1755388800000},"content-version":"vor","delay-in-days":47,"URL":"http:\/\/creativecommons.org\/licenses\/by-nc-nd\/4.0\/"},{"start":{"date-parts":[[2025,7,1]],"date-time":"2025-07-01T00:00:00Z","timestamp":1751328000000},"content-version":"tdm","delay-in-days":0,"URL":"http:\/\/doi.wiley.com\/10.1002\/tdm_license_1.1"}],"content-domain":{"domain":["alz-journals.onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["A&amp;amp;D Transl Res &amp;amp; Clin Interv"],"published-print":{"date-parts":[[2025,7]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                  <jats:sec>\n                    <jats:title>INTRODUCTION<\/jats:title>\n                    <jats:p>Assessment of short\u2010term intra\u2010 and inter\u2010individual variability for Alzheimer's disease (AD) plasma biomarkers is essential for clinically relevant interpretation of biomarker levels. We hypothesized that the variability of plasma tau phosphorylated at threonine 217 (p\u2010tau217) could be reduced by combining it with a tau marker, plasma brain\u2010derived tau (BD\u2010tau), as the p\u2010tau217\/BD\u2010tau ratio.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>METHODS<\/jats:title>\n                    <jats:p>Three consecutive blood samples were collected from memory clinic patients within 36 days. Patients were dichotomized by cerebrospinal fluid (CSF) amyloidosis (A\u03b2+ = 29, A\u03b2\u2212 = 18). We compared intra\u2010 and inter\u2010individual variability (coefficient of variation [CV]) in the plasma p\u2010tau217\/BD\u2010tau ratio with p\u2010tau217 alone and tested if kidney function, glycated hemoglobin, and body mass index (BMI) affected the variability. Finally, we compared the p\u2010tau217\/BD\u2010tau ratio with CSF p\u2010tau217.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>RESULTS<\/jats:title>\n                    <jats:p>\n                      We found that for A\u03b2+ individuals, the intra\u2010individual variability of the plasma p\u2010tau217\/BD\u2010tau ratio (CV 7.1% [95% confidence interval {CI} 5.6;8.4]) was lower than for p\u2010tau217 alone (CV 9.4% [95% CI 7.4;11.5]). At the group level, the variability in the p\u2010tau217\/BD\u2010tau ratio was reduced in both A\u03b2+ (CV 15.1% [95% CI 11.7;18.7]) and A\u03b2\u2212 (CV 18.4% [95% CI 13.0;23.8]) individuals compared to p\u2010tau217 alone (A\u03b2+ CV 19.1 [15.0;23.4], A\u03b2\u2212 27.1 [18.4;36.0]). Adjusting for estimated glomerular filtration rate, hemoglobin A1C, and BMI further reduced the inter\u2010individual variability of p\u2010tau217\/BD\u2010tau in the A\u03b2+ group. CSF p\u2010tau217 showed higher correlation with plasma p\u2010tau217\/BD\u2010tau (rho\u00a0=\u00a00.53,\n                      <jats:italic>p<\/jats:italic>\n                      \u00a0=\u00a00.0005) than with p\u2010tau217 alone (rho = 0.37,\n                      <jats:italic>p<\/jats:italic>\n                      = 0.02).\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>DISCUSSION<\/jats:title>\n                    <jats:p>Our findings suggest that using the ratio of plasma p\u2010tau217 to plasma BD\u2010tau and accounting for the influence of peripheral confounders improves biomarker stability, which is important for the interpretation of longitudinal biomarker changes and to prevent misclassification.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>HIGHLIGHTS<\/jats:title>\n                    <jats:p>\n                      <jats:list list-type=\"bullet\">\n                        <jats:list-item>\n                          <jats:p>The plasma p\u2010tau217\/BD\u2010tau ratio lowered short\u2010term intra\u2010 and, especially, inter\u2010individual variability compared to the variability in plasma p\u2010tau217 alone.<\/jats:p>\n                        <\/jats:list-item>\n                        <jats:list-item>\n                          <jats:p>Plasma BD\u2010tau did not correlate with eGFR, HbA1c, or BMI, while plasma p\u2010tau217 was significantly negatively associated with BMI.<\/jats:p>\n                        <\/jats:list-item>\n                        <jats:list-item>\n                          <jats:p>Adjusting for eGFR, HbA1c, and BMI further reduced the inter\u2010individual variability of p\u2010tau217\/BD\u2010tau.<\/jats:p>\n                        <\/jats:list-item>\n                        <jats:list-item>\n                          <jats:p>Additionally, CSF p\u2010tau217 correlated better with plasma p\u2010tau217\/BD\u2010tau than with p\u2010tau217 alone.<\/jats:p>\n                        <\/jats:list-item>\n                      <\/jats:list>\n                    <\/jats:p>\n                  <\/jats:sec>","DOI":"10.1002\/trc2.70143","type":"journal-article","created":{"date-parts":[[2025,8,17]],"date-time":"2025-08-17T07:16:53Z","timestamp":1755415013000},"update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":5,"title":["The plasma p\u2010tau217\/BD\u2010tau ratio improves biomarker short\u2010term variability in memory clinic patients"],"prefix":"10.1002","volume":"11","author":[{"given":"Frederikke Kragh","family":"Clemmensen","sequence":"first","affiliation":[{"name":"Danish Dementia Research Centre, Department of Neurology Copenhagen University Hospital, Rigshospitalet Copenhagen 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