The availability of quantitative measures of chronic pain that are valid and reliable in clinical patients is crucial for the development and testing of interventions (eg, drugs or surgical procedures) designed to reduce such pain. Studies designed to test the efficacy of interventions intended to decrease chronic pain in companion dogs with osteoarthritis have relied heavily on a veterinarian's assessment of lameness supported by values generated through the use of force plate gait analysis. When properly collected, gait analysis data offer an objective measure that can be reliably monitored over time; however, it can be an extremely time-consuming process, requires specialized equipment, and relies on relatively strict inclusion criteria. In addition, these measures only evaluate an animal at 1 specific time point and outside of its typical environment, and weight bearing on an affected limb is only 1 part of the much larger picture of chronic pain in companion dogs with osteoarthritis.1–5 A detailed behavior-based assessment of chronic pain performed by the owner is routinely relied on when making clinical decisions and offers the advantages of an extended assessment of a dog in its typical environment by someone who is most knowledgeable about its behavior. Although an owner's detailed assessment can be quite useful, few programs have reported the development of an owner-completed questionnaire for use as an outcome assessment tool in clinical studies.6–13
In response to this need, the CBPI was developed as an owner-completed questionnaire designed to quantify the severity and impact of chronic pain in companion dogs with osteoarthritis.6 The CBPI contains 4 questions pertaining to the severity of pain evident in a dog (the responses for these questions can be used to calculate a mean value that can provide a pain severity score) and 6 questions pertaining to how the pain interferes with the dog's typical activities (the responses to these question can be used to calculate a mean value that can provide a pain interference score).a The CBPI was created by use of standard methods for the stepwise development of a health-assessment questionnaire.14–16 Questions were generated through information gathered from focus groups of owners and an expert panel of veterinarians, and the final questionnaire was subjected to factor-analysis, reliability, and validity testing.6 Although the CBPI had excellent psychometric (reliability and validity) properties, assessment of validity and reliability alone are not sufficient to suggest that a questionnaire would be useful in quantifying the health status of an animal. The questionnaire must also be able to detect changes in the animal's condition that are the result of an intervention (eg, medication or surgery), disease progression, or resolution of the condition.14–16
The ability to detect change is the property of the questionnaire referred to as responsiveness. The objective of the study reported here was to test the responsiveness of the CBPI by determining whether it could detect changes in dogs with osteoarthritis after treatment with an intervention of known efficacy. The hypothesis was that within the context of a double-blind, randomized, placebo-controlled clinical trial, the CBPI could be used to detect substantial improvements in pain severity and pain interference scores in osteoarthritic dogs treated with an FDA-approved NSAID and would detect little improvement in scores for osteoarthritic dogs treated with a placebo.
Canine Brief Pain Inventory
Intention to treat
Stata, version 8, StataCorp, College Station, Tex.
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