Responsiveness of the Intermittent and Constant Osteoarthritis Pain (ICOAP) scale
in a trial of duloxetine for treatment of osteoarthritis knee pain.
Author(s): Risser RC(1), Hochberg MC, Gaynor PJ, D'Souza DN, Frakes EP.
Affiliation(s): Author information:
(1)Eli Lilly and Company, Indianapolis, IN, USA. Electronic address:
risser_richard_c@lilly.com.
Publication date & source: 2013, Osteoarthritis Cartilage. , 21(5):691-4
OBJECTIVE: To assess the change in the Intermittent and Constant Osteoarthritis
Pain (ICOAP)-scale scores in patients taking duloxetine or placebo and to
characterize the responsiveness of the ICOAP by comparing the effect size
associated with its scales to effect sizes seen with other pain scales used in
this study.
METHODS: This was a secondary analysis of data from a 10-week, double-blind,
randomized, flexible-dose, placebo-controlled trial that enrolled patients who
had persistent moderate pain due to osteoarthritis (OA) of the knee, despite
having received nonsteroidal anti-inflammatory drug (NSAID) therapy. The pain
measures used in this study (focusing on the drug-placebo difference at week 8)
were patient-rated pain severity, the Western Ontario and McMaster Universities
Osteoarthritis Index (WOMAC), the Brief Pain Inventory (BPI), and the ICOAP.
RESULTS: The mean difference between duloxetine and placebo at week 8 for
patient-rated pain severity, the BPI average pain, WOMAC pain, and each ICOAP
scale was statistically significant (P < 0.001 for each). The ICOAP total showed
a moderate effect size of 0.53, whereas the constant and intermittent scores
showed effect sizes of 0.47 and 0.49, respectively. The patient-rated pain
severity and the BPI average pain showed similar moderate effect sizes of 0.59
and 0.53, respectively.
CONCLUSION: The study demonstrated efficacy of duloxetine compared with placebo
when using the ICOAP scale in a placebo-controlled trial. The observed treatment
effect size for the ICOAP scores was similar to that for other reliable, valid
and responsive pain assessments.
CLINICAL TRIALS REGISTRATION: ClinicalTrial.gov Identifier: NCT01018680.
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