Optimizing Pain Intensity Assessment in Clinical Trials: How Many Ratings are Needed to Best Balance the Need for Validity and to Minimize Assessment Burden?

Pain intensity is the most commonly used outcome domain in pain clinical trials. To minimize the chances of type II error (ie, concluding that a treatment does not have beneficial effects, when in fact it does), the measure of pain intensity used should be sensitive to changes produced by effective pain treatments. Here we sought to identify the combination of pain intensity ratings that would balance the need for reliability and validity against the need to minimize assessment burden. We conducted secondary analyses using data from a completed 4-arm clinical trial of psychological pain treatments (N = 164 adults). Current, worst, least, and average pain intensity in the past 24 hours were assessed 4 times before and after treatment using 0 to 10 numerical rating scale-11. We created a variety of composite scores using these ratings and evaluated their reliability (Cronbach's alphas) and validity (ie, associations with a gold standard score created by averaging 16 ratings and sensitivity for detecting between-group differences in treatment efficacy). We found that for each measure, reliability increased as the number of ratings used to create the measures increased and that ratings from 3 or more days were needed to have adequately strong associations with the gold standard. Regarding sensitivity, the findings suggest that composite scores made up of ratings from 4 days are needed to maximize the chances of detecting treatment effects, especially with smaller sample sizes. In conclusion, using data from 3 or 4 days of assessment may be the best practice. PERSPECTIVE: Composite scores made up of at least 3 days of pain ratings appear to be needed to maximize reliability and validity while minimizing the assessment burden. TRIAL REGISTRATION: clinicaltrials.gov NCT01800604.

Pharmacotherapy for Spine-Related Pain in Older Adults

As the population ages, spine-related pain is increasingly common in older adults. While medications play an important role in pain management, their use has limitations in geriatric patients due to reduced liver and renal function, comorbid medical problems, and polypharmacy. This review will assess the evidence basis for medications used for spine-related pain in older adults, with a focus on drug metabolism and adverse drug reactions. A PubMed/OVID search crossing common spine, neck, and back pain terms with key words for older adults and geriatrics was combined with common drug classes and common drug names and limited to clinical trials and age over 65 years. The results were then reviewed with identification of commonly used drugs and drug categories: nonsteroidal anti-inflammatories (NSAIDs), acetaminophen, corticosteroids, gabapentin and pregabalin, antispastic and antispasmodic muscle relaxants, tricyclic antidepressants (TCAs), serotonin-norepinephrine reuptake inhibitors (SNRIs), tramadol, and opioids. Collectively, 138 double-blind, placebo-controlled trials were the focus of the review. The review found a variable contribution of high-quality studies examining the efficacy of medications for spine pain primarily in the geriatric population. There was strong evidence for NSAID use with adjustments for gastrointestinal and renal risk factors. Gabapentin and pregabalin had mixed evidence for neuropathic pain. SNRIs had good evidence for neuropathic pain and a more favorable safety profile than TCAs. Tramadol had some evidence in older patients, but more so in persons aged < 65 years. Rational therapeutic choices based on geriatric spine pain diagnosis are helpful, such as NSAIDs and acetaminophen for arthritic and myofascial-based pain, gabapentinoids or duloxetine for neuropathic and radicular pain, antispastic agents for myofascial-based pain, and combination therapy for mixed etiologies. Tramadol can be well tolerated in older patients, but has risks of cognitive and classic opioid side effects. Otherwise, opioids are typically avoided in the treatment of spine-related pain in older adults due to their morbidity and mortality risk and are reserved for refractory severe pain. Whenever possible, beneficial geriatric spine pain pharmacotherapy should employ the lowest therapeutic doses with consideration of polypharmacy, potentially decreased renal and hepatic metabolism, and co-morbid medical disorders.

Efficacy of duloxetine in patients with knee osteoarthritis or chronic low back pain with early pain reduction: An exploratory post-hoc analysis of Japanese phase 3, 1-year extension studies

BACKGROUND

Two previous phase 3, double-blind, randomized, placebo-controlled trials showed that duloxetine 60 mg/day for 14 weeks significantly improved pain and quality of life in Japanese patients with knee osteoarthritis or chronic low back pain. In their open-label extension studies, these improvements were maintained for ≥48 weeks. This post-hoc analysis assessed the relationship between initial response to duloxetine and long-term pain reduction and quality of life in patients with knee osteoarthritis or chronic low back pain.

METHODS

Patients (knee osteoarthritis: N = 43; chronic low back pain: N = 41) were subdivided based on extent of pain reduction from baseline to Week 4 of duloxetine (≥30%, 10-30%, or <10% reduction in Brief Pain Inventory-Severity average pain score). Outcome measures were changes from baseline for Brief Pain Inventory-Severity and Brief Pain Inventory-Interference at regular intervals up to Week 65.

RESULTS

Mean change from baseline in Brief Pain Inventory-Severity was greater in patients with ≥30% early pain reduction than in patients with <10% early pain reduction through Week 27 for both conditions, and also Weeks 47-65 for back pain. Compared with the <10% early pain reduction group, mean change from baseline in the average of seven Brief Pain Inventory-Interference domain scores was greater in the ≥30% or 10-30% early pain reduction groups for knee osteoarthritis (except Weeks 63-65), and in the ≥30% early pain reduction group for chronic low back pain through Week 19.

CONCLUSIONS

These results suggest that patients with knee osteoarthritis who respond well to duloxetine in the first month might experience sustained, long-term pain relief with generally greater quality-of-life improvement than patients with poor initial response. Patients with chronic low back pain who had strong initial response may experience a greater long-term pain relief, but not greater quality-of-life improvement, than patients with poor initial response.