Article Text

Download PDFPDF

Man versus machine: comparison of naked-eye estimation and quantified capillary refill
  1. Rani Toll John1,2,
  2. Joakim Henricson2,3,
  3. Chris D Anderson4,5,
  4. Daniel Björk Wilhelms2,3
  1. 1 Division of Cell Biology, Department of Clinical and Experimental Medicine, Faculty of Health Sciences, Linköping University, Linköping, Östergötland, Sweden
  2. 2 Department of Emergency Medicine, Local Health Care Services in Central Östergötland, Region Östergötland, Linköping, Sweden
  3. 3 Division of Drug Research, Department of Medical and Health Sciences, Faculty of Health Sciences, Linköping University, Linköping, Sweden
  4. 4 Division of Cell Biology, Department of Clinical and Experimental Medicine, Faculty of Health Sciences, Linköping University, Linköping, Östergötland, Sweden
  5. 5 Department of Dermatology and Venerology, Heart and Medicine Centre, Region Östergötland, Linköping, Sweden
  1. Correspondence to Dr Rani Toll John, Division of Cell Biology Department of Clinical and Experimental Medicine, Faculty of Health Sciences, Linköping University Linköping Östergötland Sweden; ranitoll{at}


Background Capillary refill (CR) time is traditionally assessed by ‘naked-eye’ inspection of the return to original colour of a tissue after blanching pressure. Few studies have addressed intra-observer reliability or used objective quantification techniques to assess time to original colour. This study compares naked-eye assessment with quantified CR (qCR) time using polarisation spectroscopy and examines intra-observer and interobserver agreements in using the naked eye.

Method A film of 18 CR tests (shown in a random fixed order) performed in healthy adults was assessed by a convenience sample of 14 doctors, 15 nurses and 19 secretaries (Department of Emergency Medicine, Linköping University, September to November 2017), who were asked to estimate the time to return to colour and characterise it as ‘fast’, ‘normal’ or ‘slow’. The qCR times and corresponding naked-eye time assessments were compared using the Kruskal-Wallis test. Three videos were shown twice without observers’ knowledge to measure intra-observer repeatability. Intra-observer categorical assessments were compared using Cohen’s Kappa analysis. Interobserver repeatability was measured and depicted with multiple-observer Bland-Altman plotting. Differences in naked-eye estimation between professions were analysed using ANOVA.

Results Naked-eye assessed CR time and qCR time differ substantially, and agreement for the categorical assessments (naked-eye assessment vs qCR classification) was poor (Cohen’s kappa 0.27). Bland-Altman intra-observer repeatability ranged from 6% to 60%. Interobserver agreement was low as shown by the Bland-Altman plotting with a 95% limit of agreement with the mean of ±1.98 s for doctors, ±1.6 s for nurses and ±1.75 s for secretaries. The difference in CR time estimation (in seconds) between professions was not significant.

Conclusions Our study suggests that naked-eye-assessed CR time shows poor reproducibility, even by the same observers, and differs from an objective measure of CR time.

  • acute care
  • clinical assessment
  • emergency department management
  • trauma
  • resuscitation

This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See:

Statistics from

Request Permissions

If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.


  • Contributors DBW and RTJ conceived the study. DBW, RTJ and JH designed the trial. DBW obtained research funding. DBW and CDA supervised the conduct of the trial. RTJ and JH undertook recruitment of observers and managed the data with assistance from DBW. DBW and RTJ drafted the manuscript, and all authors contributed substantially to its revision. RTJ takes responsibility for the paper as a whole.

  • Funding This work was supported by two grants from Region Östergötland to author DBW (LIO-532001 and LIO-700271).

  • Competing interests RTJ and DBW have no conflicts of interest to declare. The bioengineering method TiVi is marketed by the company WheelsBridge AB. No financial support from WheelsBridge AB was involved in the conduct of the study. JH is employed by the Östergötland County Council but has a royalty agreement with WheelsBridge AB. CDA has a full-time academic position but also limited involvement in WheelsBridge AB.

  • Ethics approval This study was reviewed and approved by the Regional Ethical Vetting Board in Linköping, Sweden (permit number M200-07).

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Patient consent for publication Not required.