The validity, reliability and minimal clinically important difference of the patient specific functional scale in snake envenomation

PLoS One. 2019 Mar 5;14(3):e0213077. doi: 10.1371/journal.pone.0213077. eCollection 2019.

Abstract

Objective: Valid, reliable, and clinically relevant outcome measures are necessary in clinical studies of snake envenomation. The aim of this study was to evaluate the psychometric (validity and reliability) and clinimetric (minimal clinically important difference [MCID]) properties of the Patient-Specific Functional Scale (PSFS) in snakebite envenomation.

Methods: We performed a secondary analysis of two existing snakebite trials that measured clinical outcomes using the PSFS as well as other quality of life and functional assessments. Data were collected at 3, 7, 10, and 17 days. Reliability was determined using Cronbach's alpha for internal consistency and the intraclass correlation coefficient (ICC) for temporal stability at 10 and 17 days. Validity was assessed using concurrent validity correlating with the other assessments. The MCID was evaluated using the following criteria: (1) the distribution of stable patients according to both standard error of measurement (SEM) and responsiveness techniques, and (2) anchor-based methods to compare between individuals and to detect discriminant ability of a positive change with a receiver operator characteristic (ROC) curve and optimal cutoff point.

Results: A total of 86 patients were evaluated in this study. The average PSFS scores were 5.37 (SD 3.23), 7.95 (SD 2.22), and 9.12 (SD 1.37) at 3, 7, and 10 days, respectively. Negligible floor effect was observed (maximum of 8% at 3 days); however, a ceiling effect was observed at 17 days (25%). The PSFS showed good reliability with an internal consistency of 0.91 (Cronbach's alpha) (95% CI 0.88, 0.95) and a temporal stability of 0.83 (ICC) (95% CI 0.72, 0.89). The PSFS showed a strong positive correlation with quality of life and functional assessments. The MCID was approximately 1.0 for all methods.

Conclusions: With an MCID of approximately 1 point, the PSFS is a valid and reliable tool to assess quality of life and functionality in patients with snake envenomation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Antivenins / therapeutic use*
  • Female
  • Humans
  • Immunoglobulin Fab Fragments / therapeutic use*
  • Male
  • Middle Aged
  • Minimal Clinically Important Difference
  • Multicenter Studies as Topic
  • Observational Studies as Topic
  • Outcome Assessment, Health Care
  • Psychometrics
  • Quality of Life
  • ROC Curve
  • Randomized Controlled Trials as Topic
  • Reproducibility of Results
  • Snake Bites / drug therapy*
  • Treatment Outcome
  • United States
  • Young Adult

Substances

  • Antivenins
  • Crotalidae Polyvalent immune Fab
  • Immunoglobulin Fab Fragments

Grants and funding

The parent studies from which data were derived, were funded by BTG International Inc. The authors received no specific funding for this work.