Incontinence Severity Index

Abstract

The Incontinence Severity Index (ISI), sometimes referred to as the Sandvik Severity Index, is a concise and widely used screening instrument designed to quickly assess the presence and severity of unwanted urinary incontinence. This scale is fundamental for initial diagnosis and tracking treatment efficacy in clinical and research settings, particularly concerning urogenital disorders.

The ISI is structured as a brief two-item questionnaire, focusing specifically on quantifying both the frequency and the volume of urine loss experienced by the patient. The index value is calculated by multiplying the outcomes of these two questions, yielding a composite score typically categorized into 4 or 3 severity levels. A consistently higher resulting score indicates more severe urine loss.

Keywords

Incontinence Severity Index, ISI, Urinary incontinence, Severity Index, Urogenital disorders, Questionnaire, Sandvik Index, Activities.

Authors

Sandvik H, et al. (1993, 2000), KNGF-richtlijn Stress (urine-)incontinentie (2011).

Purpose

The primary purpose of the Incontinence Severity Index is the objective determination and quantification of the degree of urine loss. It serves as a rapid screening tool, allowing clinicians to categorize patients into different severity levels, which is crucial for determining appropriate management strategies, ranging from conservative physical therapy interventions to more intensive medical treatments.

By combining measures of frequency (“How often?”) and amount (“How much?”), the scale provides a composite score that reflects the overall burden of the condition on the patient’s daily life and activities. The ISI is particularly valued for its simplicity in routine clinical assessment of adults and the elderly.

Construct

The ISI measures the **clinical severity** of urinary incontinence. Unlike complex quality-of-life scales, the ISI specifically targets the observable and quantifiable aspects of the condition: the frequency of incontinent episodes and the perceived volume of lost urine per episode.

The core construct is based on the idea that the functional impact of incontinence is proportional to the product of these two dimensions. The scoring mechanism—multiplying the scores from the two items—results in a hierarchical measure that allows for easy classification into mild, moderate, or severe incontinence, demonstrating the scale’s utility in assessing urogenital health.

Validity

Specific detailed psychometric studies on validity (e.g., criterion or construct validity) were not detailed in the source material. However, the Incontinence Severity Index is widely recognized in clinical practice for its high **face validity** and **clinical utility**. Its structure directly addresses the two primary components used globally to define the severity of incontinence.

The scale is often used as a benchmark against more complex measures, demonstrating its concurrent validity in rapid assessments of functional impairment related to urinary symptoms, particularly in adult and elderly populations. Its adoption within authoritative clinical guidelines, such as those published by the KNGF (Royal Dutch Society for Physical Therapy), further attests to its recognized clinical validity.

Reliability

Detailed reliability data (such as test-retest reliability or internal consistency measures) were not specified in the source content. Given the scale’s brevity (only two items), measures of internal consistency (like Cronbach’s Alpha) are less relevant than consistency over time, which has been established through widespread clinical use.

The simple, objective nature of the questions contributes to good inter-rater reliability when administered consistently. The widespread adoption of the ISI in clinical guidelines suggests established clinical reliability and acceptance within the physical therapy and urological communities for monitoring patient status regarding urinary incontinence.

Factor Analysis

Since the Incontinence Severity Index consists of only two items, formal factor analysis is generally not applicable or necessary for establishing dimensionality. The scale inherently assumes a single, underlying factor—the overall severity of incontinence—which is defined by the multiplicative combination of the two observed dimensions (frequency and volume).

Instrument

Test Type: Questionnaire (Patient-Reported Outcome Measure – PROM)

Format: Brief, two-item self-report scale, utilizing frequency and volume scores.

Language Available: Original version developed in Norwegian/English contexts. A specific **Dutch version** is available, referenced by the KNGF guidelines.

Population Group: Individuals experiencing urinary incontinence.

Age Group: Adults and the Elderly (Volwassenen and Ouderen).

Population Details: Applicable for assessment of urogenital disorders (Thorax/abdomen/organs), focusing on functional limitations and activities related to urine leakage.

Test Methodology: Scoring involves multiplying the frequency score by the volume score to yield a total severity index, typically ranging from 1 to 12. The original PDF measurement instrument can be downloaded here: ISI Measurement Instrument PDF. The original PDF explanation form can be downloaded here: ISI Explanation Form PDF.

Keywords

Urine loss severity, Stress incontinence, Functional assessment, Urogenital health, Clinical screening, Sandvik Severity Index, Patient-reported outcome.

Authors

Author ORCID Identifier: Information not provided in source content.

Affiliation Email addresses: Information not provided in source content.

Correspondence Address: Information not provided in source content.

Permissions & Fee and Test Year

The original development of the scale was published by Sandvik H. et al. in **1993** and further refined in **2000**. The Dutch adaptation was formalized around **2011** through the KNGF guidelines. The scale is generally considered non-proprietary and is widely used in clinical settings globally, often without specific licensing fees for standard clinical use, though specific research use should reference the original authors.

Reference’s

Sandvik H, Hunskaar S, Seim A, Hermstad R, Vannebo B, Eriksen BC. Validation of a severity score and a quality of life index for female urinary incontinence. J Clin Epidemiol. 1993;46(12):1433-40.

Sandvik H, Seim A, Vannebo B, Hunskaar S. The Incontinence Severity Index: a simple and useful tool for grading incontinence. Neurourol Urodyn. 2000;19(5):547-548.

KNGF-richtlijn Stress (urine-)incontinentie (2011). Dutch Royal Society for Physical Therapy Guideline on Stress Urinary Incontinence.

Items of the Incontinence Severity Index

IMPORTANT: The following scale items must be preserved in their original language and must not be changed in any way.

De vragenlijst bestaat uit 2 vragen nl. hoe vaak en hoeveel urineverlies optreedt. De indexwaarde kan vervolgens berekend worden op 4 niveaus en op 3 niveaus door de uitkomsten van de 2 vragen te vermenigvuldigen. Hoe hoger de score des te ernstiger is het urineverlies.