Validity, reliability and acceptability of the Imperial Nutritional Screening System (INSYST) : A tool that does not require the body mass index

Abstract

Background: Nutritional screening tools are central to identifying malnourished patients, but their efficacy is often reduced as a result of difficulties in obtaining height for body mass index (BMI) calculations. The present study aimed to evaluate the validity, reliability and acceptability of the Imperial Nutritional Screening System (INSYST); a tool that does not require the BMI. Methods: Patients were screened by the researcher within 72 h of admission using INSYST I & II, Malnutrition Universal Screening Tool (MUST) and Mini Nutritional Assessment (MNA), including taking height and weight. Routine INSYST data, completed by nursing staff, were subsequently collected. At risk and malnourished patients were combined for statistical analysis. Inter-tool and inter-rater agreement (kappa, κ) was evaluated. Sensitivity and specificity were calculated. Nurses were timed using INSYST. Acceptability, including ease and speed of use, was evaluated. Results: Kappa (agreement) scores (all P <0.001) were substantial for INSYST I versus MUST and MNA (κ = 0.73 and κ = 0.76, respectively) and moderate for INSYST II (both κ = 0.53). The sensitivity of INSYST I and II was high (95-100%), whereas specificity was lower (65-83%). The agreement between dietitian and nurse for INSYST I was substantial κ = 0.77 and that for INSYST II was fair κ = 0.39 (both P ≤ 0.001). There was little disagreement for INSYST I, although nurses tended to underestimate malnutrition risk when using INSYST II. INSYST I took a median of 60 s to complete, INSYST II took 102 s and weighing took 100 s, giving a total time of approximately 5 min. Likert scales showed that the majority of nurses scored INSYST as being fast and easy to use. Conclusions: INSYST has shown promising levels of concurrent validity (versus MUST and MNA), inter-rater reliability and acceptability, suggesting that BMI (and therefore height) is unnecessary for identifying malnourished patients.