What is the Interstitial Cystitis (IC) Symptom Index?

Interstitial Cystitis Symptom Index (ICSI)

The Interstitial Cystitis Symptom Index (ICSI), also known as the O'Leary-Sant Symptom Index, is a validated 4-item self-administered questionnaire that measures the cardinal symptoms of interstitial cystitis/bladder pain syndrome (urgency, frequency, nocturia, and pain/burning), with scores ranging from 0-20. 1, 2

Structure and Components

• The ICSI contains 4 items that specifically assess: urgency (strong need to urinate with little or no warning), frequency of urination, nighttime urination (nocturia), and pain or burning sensations 3
• Each item is scored individually, and the total ICSI score is calculated as the sum of all item scores, with a possible range of 0-20 points 3
• The questionnaire asks patients how often each symptom is experienced, using a frequency-based rating scale 4

Psychometric Properties and Validation

• The ICSI demonstrates excellent internal consistency reliability (Cronbach alpha), good test-retest reliability (intraclass correlation coefficient), and strong construct validity 3
• The instrument is responsive to change, with patients reporting 75% improvement showing a 48% mean reduction in ICSI scores, and those reporting 100% improvement demonstrating a 77% mean reduction 3
• The ICSI has excellent discriminatory ability between patients with IC/BPS and healthy controls 2
• The ICSI correlates strongly (r = 0.80) with the University of Wisconsin Symptom Instrument, another validated IC assessment tool 5

Clinical Applications

• The American Urological Association recommends documenting baseline symptoms using validated tools such as the ICSI to measure treatment effects in patients with IC/BPS 6
• The ICSI should be utilized in clinical trials and treatment outcome studies to provide reliable, validated, and reproducible outcome measures 3, 2
• The questionnaire is particularly useful for monitoring symptom changes over time during therapeutic interventions 3

Companion Instrument

• The ICSI is typically paired with the IC Problem Index (ICPI), which assesses how problematic each symptom is for the patient 2
• The ICSI and ICPI scores correlate strongly (r = 0.83), though there are relevant differences in how symptom severity correlates with associated problems 5
• Among the symptom-problem pairs, urgency correlates best (r = 0.84), followed by nocturia (r = 0.82), pain (r = 0.70), and frequency (r = 0.68) 5

Important Limitations and Caveats

• The ICSI urgency question ("strong need to urinate with little or no warning") may underestimate the prevalence and degree of urgency compared to severity-based questions about "compelling urge to urinate that is difficult to postpone" 4
• Some patients deny urgency on the ICSI question yet report intense urgency when asked about severity, suggesting the sudden urgency descriptor does not capture the full spectrum of urgency experienced by IC/BPS patients 4
• While the ICSI distinguishes IC/BPS from other urinary tract pathologies, it lacks sufficient specificity to serve as the sole diagnostic indicator and should not be used alone to define IC/BPS 7
• The questionnaire is best used to screen patients with urinary tract symptoms to identify those requiring further examination or to follow patients already diagnosed with IC/BPS 7