A comparison of venous versus capillary measurements of drug concentration

John E. Murphy, Tim Peltier, Doug Anderson, Earl S. Ward

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


Accessing patient’s veins for drug level sampling is not always feasible. The use of capillary sampling techniques is often utilized when venous access is hampered. In the therapeutic monitoring of patients, unexpected drug level results often occur that can be caused by a number of different factors. The possibility that differences in assay results might occur if samples were collected by capillary stick vs. venous phlebotomy was examined by simultaneous sampling in 18 patients. Although correlation was very high (0.999) and percentage differences fairly low (range of 0 to 15.4%), a statistical difference was noted in the sampling methods. The precision was 6.5 ± 6.58% and there was a slight negative bias (-3.76%), with capillary samples less than venous samples. Although there were statistical differences for the drugs studied in the concentration ranges evaluated, capillary samples should provide fairly small errors when compared to venous samples.

Original languageEnglish (US)
Pages (from-to)264-267
Number of pages4
JournalTherapeutic Drug Monitoring
Issue number3
StatePublished - May 1990
Externally publishedYes


  • Assays
  • Capillary venous comparison
  • Drug levels

ASJC Scopus subject areas

  • Pharmacology
  • Pharmacology (medical)


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