{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,24]],"date-time":"2026-04-24T05:00:06Z","timestamp":1777006806514,"version":"3.51.4"},"reference-count":20,"publisher":"MDPI AG","issue":"4","license":[{"start":{"date-parts":[[2026,4,16]],"date-time":"2026-04-16T00:00:00Z","timestamp":1776297600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Pharmaceuticals"],"abstract":"<jats:p>Background\/Objectives: Therapeutic drug monitoring (TDM) of immunosuppressants is essential in treating pediatric kidney diseases; however, repeated venipuncture is burdensome in children. We evaluated whether minimally invasive fingerstick capillary sampling combined with liquid chromatography\u2013tandem mass spectrometry (LC-MS\/MS) provides results analytically comparable to those of conventional venous sampling. Methods: Capillary whole blood (2.8 \u00b5L) was collected via fingersticks from pediatric patients receiving mycophenolate mofetil, with or without tacrolimus (TAC) or cyclosporine A (CsA). Drug concentrations were quantified using a previously validated simultaneous LC-MS\/MS method and compared with conventional venous sampling using linear regression and Bland\u2013Altman analyses. Results: Seventy-four paired samples from 21 patients were analyzed. Strong correlations were observed between capillary and venous samples for mycophenolic acid (MPA), TAC, and CsA (R2 &gt; 0.90). Hematocrit correction improved agreement for MPA. Bland\u2013Altman analyses demonstrated acceptable bias across analytes. Conclusions: Fingerstick-based microvolume sampling combined with LC-MS\/MS provides analytically reliable immunosuppressant quantification in pediatric patients. Although larger clinical validation is required, this minimally invasive approach may reduce procedural burden and may support future outpatient or home-based TDM strategies.<\/jats:p>","DOI":"10.3390\/ph19040630","type":"journal-article","created":{"date-parts":[[2026,4,16]],"date-time":"2026-04-16T15:14:12Z","timestamp":1776352452000},"page":"630","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Minimally Invasive Therapeutic Drug Monitoring of Immunosuppressants in Children with Kidney Diseases: Validation of Fingerstick Sampling Using LC-MS\/MS"],"prefix":"10.3390","volume":"19","author":[{"ORCID":"https:\/\/orcid.org\/0009-0004-7335-7286","authenticated-orcid":false,"given":"Marika","family":"Ishii","sequence":"first","affiliation":[{"name":"Department of Pediatrics, Jichi Medical University, 3311-1 Yakushiji, Shimotsuke 329-0498, Tochigi, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jun","family":"Aoyagi","sequence":"additional","affiliation":[{"name":"Department of Pediatrics, Jichi Medical University, 3311-1 Yakushiji, Shimotsuke 329-0498, Tochigi, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Natsuka","family":"Kimura","sequence":"additional","affiliation":[{"name":"Department of Translational Research, Clinical Research Center, Jichi Medical University Hospital, 3311-1 Yakushiji, Shimotsuke 329-0498, Tochigi, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Masanori","family":"Kurosaki","sequence":"additional","affiliation":[{"name":"Department of Pediatrics, Jichi Medical University, 3311-1 Yakushiji, Shimotsuke 329-0498, Tochigi, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Tomomi","family":"Maru","sequence":"additional","affiliation":[{"name":"Department of Pediatrics, Jichi Medical University, 3311-1 Yakushiji, Shimotsuke 329-0498, Tochigi, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Kazuya","family":"Tanimoto","sequence":"additional","affiliation":[{"name":"Department of Pediatrics, Jichi Medical University, 3311-1 Yakushiji, Shimotsuke 329-0498, Tochigi, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Mitsuaki","family":"Yoshino","sequence":"additional","affiliation":[{"name":"Department of Pediatrics, Jichi Medical University, 3311-1 Yakushiji, Shimotsuke 329-0498, Tochigi, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Takane","family":"Ito","sequence":"additional","affiliation":[{"name":"Department of Pediatrics, Jichi Medical University, 3311-1 Yakushiji, Shimotsuke 329-0498, Tochigi, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Takahiro","family":"Kanai","sequence":"additional","affiliation":[{"name":"Department of Pediatrics, Jichi Medical University, 3311-1 Yakushiji, Shimotsuke 329-0498, Tochigi, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1320-1165","authenticated-orcid":false,"given":"Hitoshi","family":"Osaka","sequence":"additional","affiliation":[{"name":"Department of Pediatrics, Jichi Medical University, 3311-1 Yakushiji, Shimotsuke 329-0498, Tochigi, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Ryozo","family":"Nagai","sequence":"additional","affiliation":[{"name":"Jichi Medical University, 3311-1 Yakushiji, Shimotsuke 329-0498, Tochigi, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Kenichi","family":"Aizawa","sequence":"additional","affiliation":[{"name":"Department of Translational Research, Clinical Research Center, Jichi Medical University Hospital, 3311-1 Yakushiji, Shimotsuke 329-0498, Tochigi, Japan"},{"name":"Clinical Pharmacology Center, Jichi Medical University Hospital, 3311-1 Yakushiji, Shimotsuke 329-0498, Tochigi, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2026,4,16]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"257","DOI":"10.1016\/j.trac.2015.11.016","article-title":"Recent advances in therapeutic drug monitoring of immunosuppressive drugs","volume":"79","author":"Freudenberger","year":"2016","journal-title":"Trends Analyt. 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