Does weight-bearing versus non-weight-bearing pain reflect different pain mechanisms in knee osteoarthritis?: the Multicenter Osteoarthritis Study (MOST).

OBJECTIVE: Knee osteoarthritis (OA) is predominantly characterized by pain with weight-bearing activities. Pain at rest also occurs but the mechanisms for this are not clear. We evaluated the relations of nociceptive signal alterations to weight-bearing and non-weight-bearing pain in knee OA. DESIGN: We used data from a NIH-funded longitudinal cohort of older adults with or at risk of knee OA. We evaluated quantitative sensory testing (QST) measures (pressure pain threshold (PPT) at patellae and the wrist; mechanical temporal summation (TS); conditioned pain modulation (CPM)). Each WOMAC pain question was dichotomized as having at least moderate pain, and we further categorized them as weight-bearing pain and non-weight-bearing pain. We evaluated the relation of QST measures to each pain outcome using logistic regression, adjusting for potential confounders. RESULTS: 2,749 participants (5,479 knees) were included (mean age 64 ± 11, 57% female). Each SD unit decrease in patellar PPT was associated with greater odds of both weight-bearing pain (OR 1.51 (95% CI 1.27, 1.79)) and non-weight-bearing pain (OR 1.46 (1.20-1.77)), while wrist PPT was associated with greater odds of weight-bearing pain (OR 1.27 (1.15, 1.39)) but only with pain during sitting/lying (OR 1.20 (1.01, 1.43)). TS was significantly associated with greater odds of pain with walking and stairs (OR 1.11 (1.01, 1.23), 1.11 (1.03, 1.20), respectively). CPM was not associated with any pain outcomes. CONCLUSIONS: Our findings challenge the hypothesis that non-weight-bearing pain may reflect greater pain sensitization and/or inefficient CPM than weight-bearing pain in knee OA, suggesting other mechanisms are likely responsible.

The design and conduct of clinical trials to limit missing data.

This article summarizes recommendations on the design and conduct of clinical trials of a National Research Council study on missing data in clinical trials. Key findings of the study are that (a) substantial missing data is a serious problem that undermines the scientific credibility of causal conclusions from clinical trials; (b) the assumption that analysis methods can compensate for substantial missing data is not justified; hence (c) clinical trial design, including the choice of key causal estimands, the target population, and the length of the study, should include limiting missing data as one of its goals; (d) missing-data procedures should be discussed explicitly in the clinical trial protocol; (e) clinical trial conduct should take steps to limit the extent of missing data; (f) there is no universal method for handling missing data in the analysis of clinical trials - methods should be justified on the plausibility of the underlying scientific assumptions; and (g) when alternative assumptions are plausible, sensitivity analysis should be conducted to assess robustness of findings to these alternatives. This article focuses on the panel's recommendations on the design and conduct of clinical trials to limit missing data. A companion paper addresses the panel's findings on analysis methods.

Outcome measures in placebo-controlled trials of osteoarthritis: responsiveness to treatment effects in the REPORT database.

INTRODUCTION: Treatment response in randomized clinical trials (RCT) of osteoarthritis (OA) has been assessed by multiple primary and secondary outcomes, including pain, function, patient and clinician global measures of status and response to treatment, and various composite and responder measures. Identifying outcome measures with greater responsiveness to treatment is important to increase the assay sensitivity of RCTs. OBJECTIVE: To assess and compare the responsiveness of different outcome measures used in placebo-controlled RCTs of OA. SEARCH STRATEGY: The Resource for Evaluating Procedures and Outcomes of Randomized Trials database includes placebo-controlled clinical trials of pharmacologic treatments (oral, topical, or transdermal) for OA identified from a systematic literature search of RCTs published or publicly available before August 5, 2009, which was conducted using PubMed, the Cochrane collaboration, publicly-available websites, and reference lists of retrieved publications. DATA COLLECTION AND ANALYSIS: Data collected included: (1) pain assessed with single-item ratings and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain subscale; (2) patient and clinician global measures of status, improvement, and treatment response; (3) function assessed by the WOMAC function subscale; (4) stiffness assessed by the WOMAC stiffness subscale; and (5) the WOMAC and Lequesne Algofunctional Index composite outcomes. Measures were grouped according to the total number of response categories (i.e., <10 categories or ≥10 categories). The treatment effect (difference in mean change from baseline between the placebo and active therapy arms) and standardized effect size (SES) were estimated for each measure in a meta-analysis using a random effects model. RESULTS: There were 125 RCTs with data to compute the treatment effect for at least one measure; the majority evaluated non-steroidal anti-inflammatory drugs (NSAIDs), followed by opioids, glucosamine and/or chondroitin, and acetaminophen. In general, the patient-reported pain outcome measures had comparable responsiveness to treatment as shown by the estimates of treatment effects and SES. Treatment effects and SESs were generally higher for patient-reported global measures compared with clinician-rated global measures but generally similar for the WOMAC and Lequesne composite measures. CONCLUSIONS: Comparing different outcome measures using meta-analysis and selecting those that have the greatest ability to identify efficacious treatments may increase the efficiency of clinical trials of treatments for OA. Improvements in the quality of the reporting of clinical trial results are needed to facilitate meta-analyses to evaluate the responsiveness of outcome measures and to also address other issues related to assay sensitivity.

Nonsteroidal Anti-Inflammatory Drugs and Opioids in Postsurgical Dental Pain.

Postsurgical dental pain is mainly driven by inflammation, particularly through the generation of prostaglandins via the cyclooxygenase system. Thus, it is no surprise that numerous randomized placebo-controlled trials studying acute pain following the surgical extraction of impacted third molars have demonstrated the remarkable efficacy of nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen, naproxen sodium, etodolac, diclofenac, and ketorolac in this prototypic condition of acute inflammatory pain. Combining an optimal dose of an NSAID with an appropriate dose of acetaminophen appears to further enhance analgesic efficacy and potentially reduce the need for opioids. In addition to being on average inferior to NSAIDs as analgesics in postsurgical dental pain, opioids produce a higher incidence of side effects in dental outpatients, including dizziness, drowsiness, psychomotor impairment, nausea/vomiting, and constipation. Unused opioids are also subject to misuse and diversion, and they may cause addiction. Despite these risks, some dental surgical outpatients may benefit from a 1- or 2-d course of opioids added to their NSAID regimen. NSAID use may carry significant risks in certain patient populations, in which a short course of an acetaminophen/opioid combination may provide a more favorable benefit versus risk ratio than an NSAID regimen.

Oral transmucosal fentanyl citrate: randomized, double-blinded, placebo-controlled trial for treatment of breakthrough pain in cancer patients.

BACKGROUND: Patients with cancer frequently experience episodes of acute pain, i.e., breakthrough pain, superimposed on their chronic pain. Breakthrough pain is usually treated with short-acting oral opioids, most of which provide some relief after 15-20 minutes, with peak effects after 30-45 minutes. Oral transmucosal fentanyl citrate (OTFC), a unique formulation of the opioid fentanyl, has been shown to provide meaningful pain relief within 5 minutes in patients following surgery. We conducted a multicenter, randomized, double-blinded, placebo-controlled trial of OTFC for cancer-related breakthrough pain. METHODS: Patients who were 18 years of age or older, receiving the equivalent of at least 60 mg oral morphine or at least 50 microg transdermal fentanyl per day for chronic cancer-related pain, and experiencing at least one episode of breakthrough pain per day were studied. After titration to an effective OTFC dose, subjects were given 10 randomly ordered treatment units (seven OTFC units and three placebo units) in the form of identical lozenges. If acceptable pain relief was not achieved within 30 minutes, subjects were instructed to take their previous breakthrough pain medication (i.e., rescue medication). Pain intensity, pain relief, and use of rescue medication were evaluated at 15-minute intervals over a 60-minute period. RESULTS: Eighty-nine of 92 patients who received the randomized treatment were assessable (i.e., treated with at least one unit of OTFC and one unit of placebo). OTFC produced significantly larger changes in pain intensity and better pain relief than placebo at all time points (two-sided P<.0001). Episodes treated with placebo required the use of rescue medication more often than episodes treated with OTFC (34% versus 15%; relative risk = 2.27; 95% confidence interval = 1.51-3.26; two-sided P<.0001). CONCLUSIONS: OTFC appears effective in the treatment of cancer-related breakthrough pain.

Gastrointestinal tract bleeding associated with naproxen sodium vs ibuprofen.

BACKGROUND: The risk of gastrointestinal tract bleeding requiring hospitalization associated with naproxen sodium was compared with that with ibuprofen, using a prescription database to approximate over-the-counter dosing. OBJECTIVE: To evaluate the safety of naproxen sodium. METHODS: A claims database containing Ohio Medicaid data from January 1986 through February 1993 and Michigan Medicaid data from April 1983 through July 1993 was used to compare 101,318 patients dispensed naproxen sodium with 277,601 patients dispensed ibuprofen. Using a case-cohort design, all 59 patients from the full cohort who had been hospitalized with upper gastrointestinal tract bleeding (UGIB) that developed within 14 days after the first prescription for the study drugs were compared with a subcohort made up of a 10% random sample of subjects selected from the combined drug cohorts. RESULTS: The incidence of UGIB occurring within 14 days after the first prescription in the naproxen sodium cohort was 26 (0.026%) of 101,318 (95% confidence interval [CI], 0.017%-0.038%), compared with 33 (0.012%) of 277,601 patients (95% CI, 0.008%-0.017%) in the ibuprofen cohort. Overall, the use of naproxen sodium vs ibuprofen was associated with an adjusted relative risk of 2.0 (95% CI, 1.1-3.8). Among people with multiple prescriptions, the crude relative risk for those receiving therapy in a dose typical of over-the-counter use was 4.1 (95% CI, 1.2-13.8). CONCLUSIONS: The overall incidence of UGIB is low with both drugs. There is little additional absolute risk posed by the use of low-dose naproxen sodium, compared with low-dose ibuprofen, despite an increased relative risk. However, given the widespread use of these drugs, a substantial number of additional cases of UGIB could result from use of naproxen sodium. This increased risk should be considered, especially for patients whose baseline risk of UGIB is elevated.

Ethnicity influences morphine pharmacokinetics and pharmacodynamics.

OBJECTIVE: Our objective was to evaluate ethnic differences in response to morphine and to determine whether any detectable differences were pharmacokinetically based. METHODS: This cohort study was carried out in a teaching hospital. Sixty-six young, healthy male subjects from 3 ethnic groups (Caucasians, native Indians, and Latinos; n = 22 in each group) consented to participate. All subjects received an intravenous morphine bolus of 0.08 mg/kg followed by 0.002 mg/kg. min infused for 30 minutes. Respiratory response was evaluated with the carbon dioxide rebreathing method before and at 25, 95, 180, and 360 minutes after morphine administration. Vital signs and opioid side effects were recorded, and serial blood samples were analyzed for morphine, morphine-3-glucuronide, and morphine-6-glucuronide (M6G). RESULTS: All 3 groups had suppression of the ventilatory response to hypercapnia, but the degree of blunting of the ventilatory response differed among groups. Compared with Caucasians, native Indians had an additional 18% reduction in ventilatory response after morphine administration (95% confidence interval, -35% to -2%). The incidence of side effects was similar in all groups (P =.18). Caucasians had higher plasma levels of M6G than did native Indians or Latinos. M6G areas under 6-hour concentration-versus-time curve were as follows: Caucasians, 12,065 +/- 4354; native Indians, 8464 +/- 4809; and Latinos, 9156 +/- 3764 ng. min/mL (P =.03). CONCLUSIONS: Ethnicity influences the response to morphine. Native Indians are more susceptible to morphine depression of the ventilatory response than Caucasians, despite the higher serum M6G levels in Caucasians.

Response to first drug trial predicts outcome in childhood temporal lobe epilepsy.

OBJECTIVE: To construct a clinical prediction model for the early identification of children destined to develop refractory temporal lobe epilepsy (TLE) 2 years after epilepsy onset. METHODS: Patients with TLE between 1 and 18 years old seen in the Division of Neurology at Children's Hospital of Philadelphia during 1999 were identified through billing records and chart review. Data were abstracted independently on 5 candidate predictor variables for refractory TLE and on seizure frequency outcome at 2 years after epilepsy onset. RESULTS: One hundred twenty patients met inclusion criteria and had at least 2 years of follow-up. Forty-five of 120 patients (37.5%) had refractory TLE at 2 years after onset, and 75 of 120 (62.5%) were seizure free. Three significant predictors of refractory TLE were found on bivariate analysis: an early risk factor for epilepsy (risk ratio = 3.5 [95% CI 2.2, 5.6]), temporal lobe abnormality on MRI scan (2.9 [95% CI 1.9, 4.6]), and failure of the first antiepileptic drug (AED) trial (16.5 [95% CI 6.3, 43.9]). Logistic regression indicated that the best model to predict refractory TLE contained only the variable "failure of first AED trial," with a positive predictive value of 0.89 (95% CI 0.76, 0.96) and negative predictive value of 0.95 (95% CI 0.87, 0.99) to predict "refractory TLE" at 2 years. CONCLUSIONS: Failure of first AED trial accurately predicts refractory TLE at 2 years after onset, based on retrospective cohort data in children. If verified prospectively and with longer follow-up, this finding should support earlier consideration of surgical options.

Severe sudden visual loss caused by pseudotumor cerebri and lumboperitoneal shunt failure.

PURPOSE: Severe vistral acuity loss associated with pseudotumor cerebri is usually caused by chronic optic disk edema or a retinal abnormality. METHODS: We treated a women, with known pseudotumor cerebri treated with a lumboperitoneal shunt, who developed acute pallied optic disk swelling and visual acuity of R.E.: no light perception and L.E.: 20/70 in association with lumboperitoneal shunt failure. There were no contributory retinal lesions. RESULTS: The patient underwent optic nerve sheath fenestration and lumboperitoneal shunt revision. Visual acuity improved to 20/20 in both eyes. The papilledema resolved. CONCLUSION: The severe sudden visual loss was attributed to axoplasmic stasis and optic nerve ischemia associated with a sudden rise in intracranial pressure.

What is clinically meaningful: outcome measures in pain clinical trials.

OBJECTIVE: The goal of this analysis is a better understanding of the issues involved in establishing the amount of change in pain that must be reported by subjects, participating in clinical trials and using standard pain scales, to indicate a clinically important difference. DESIGN: A review of the literature and a discussion of relevant concepts are presented. The focus is on outcome measures of pain commonly used in the studies described, including pain intensity, pain relief, global assessment of the medication effect, and requirement for an extra dose of rescue medication to treat a pain episode. The standard analysis statistics used to summarize the data are the central tendency of the groups being compared (i.e., mean, median, or mode), and the proportion of subjects that achieve one or more specific levels of benefit. RESULTS: The analysis of the proportion of responders in the groups being compared allows for a more easily understandable clinical importance of the results. CONCLUSIONS: An analysis of the proportion of responders is a clinically relevant analysis for many pain clinical trials and should be presented for one or more levels of response as appropriate. This will allow the readers to more easily interpret the results and apply them to clinical practice.

Neuropathic cancer pain: the role of adjuvant analgesics.

Neuropathic pain may be defined as pain related to abnormal somatosensory processing in either the peripheral or central nervous system. This pathophysiologic label is typically applied when the painful symptom is associated with an overt injury to neural structures, is part of a recognized syndrome, or has a dysesthetic quality (usually burning, shooting, or electrical). Most neural injury does not lead to clinically important neuropathic pain, but sometimes even a small degree of tissue injury can precipitate severe pain. In the cancer population, neuropathic pain is often related to compression, direct neoplastic invasion of the peripheral nerves or spinal cord, or to a neuropathy caused by chemotherapy. To manage neuropathic pain in this population, nonopioid adjuvant drugs that are neuroactive or neuromodulatory are often needed to complement opioid therapy. The primary adjuvant analgesics are anticonvulsant and antidepressant medications, but a wide variety of other drugs are also used. To optimize analgesic therapy in patients with neuropathic pain, both opioid and adjuvant analgesics must be used effectively.

Comparison of force plate gait analysis and owner assessment of pain using the Canine Brief Pain Inventory in dogs with osteoarthritis.

BACKGROUND: Lameness assessment using force plate gait analysis (FPGA) and owner assessment of chronic pain using the Canine Brief Pain Inventory (CBPI) are valid and reliable methods of evaluating canine osteoarthritis. There are no studies comparing these 2 outcome measures. OBJECTIVE: Evaluate the relationship between CBPI pain severity (PS) and interference (PI) scores with the vertical forces of FPGA as efficacy measures in canine osteoarthritis. ANIMALS: Sixty-eight client-owned dogs with osteoarthritis (50 hind limb and 18 forelimb). METHODS: Double-blind, randomized. Owners completed the CBPI, and dogs underwent FPGA on days 0 and 14. Dogs received carprofen or placebo on days 1 through 14. The change in PS and PI scores from day 0 to 14 were compared to the change in peak vertical force (PVF) and vertical impulse (VI). RESULTS: PS and PI scores significantly decreased in carprofen- compared with placebo-treated dogs (P = .002 and P = .03, respectively). PVF and VI significantly increased in carprofen- compared with placebo-treated dogs (P = .006 and P = .02, respectively). There was no correlation or concordance between the PS or PI score changes and change in PVF or VI. CONCLUSIONS AND CLINICAL IMPORTANCE: In these dogs with hind limb or forelimb osteoarthritis, owner assessment of chronic pain using the CBPI and assessment of lameness using FPGA detected significant improvement in dogs treated with carprofen. The lack of correlation or concordance between the change in owner scores and vertical forces suggests that owners were focused on behaviors other than lameness when making efficacy evaluations in their dogs.

Suboptimal physician adherence to quality indicators for the management of gout and asymptomatic hyperuricaemia: results from the UK General Practice Research Database (GPRD).

OBJECTIVES: : To examine adherence to validated quality indicators assessing the quality of allopurinol use in the treatment of gout and asymptomatic hyperuricaemia. METHODS: We determined physician adherence in the UK General Practice Research Database (GPRD) to three validated quality indicators developed to assess the quality of allopurinol prescribing practices. These indicators were developed to assess: (i) dosing in renal impairment; (ii) concomitant use with azathioprine or 6-mercaptopurine; and (iii) use in the treatment of asymptomatic hyperuricaemia. We also examined the association of patient-level factors (sociodemographics, comorbidity, follow-up duration and concomitant medicine use) with the treatment of asymptomatic hyperuricaemia using multivariable logistic regression. RESULTS: Of the 63 105 gout patients, 185 (0.3%) were eligible for Quality Indicator 1 and 52 (0.1%) were eligible for Quality Indicator 2. There were an additional 471 patients with asymptomatic hyperuricaemia eligible for Quality Indicator 3. Rates of practice deviation for the three individual quality indicators ranged from 25 to 57%. Male sex, older age, a history of chronic renal failure, and a greater number of concomitant medications were significantly associated with increased odds of inappropriate treatment for asymptomatic hyperuricaemia. Hypertension and diuretic use were associated with lower odds of this practice. CONCLUSIONS: One-quarter to one-half of all patients eligible for at least one of the validated quality of care indicators were subject to possible allopurinol prescribing error, suggesting that inappropriate prescribing practices are widespread with this agent. Future interventions aimed at reducing inappropriate allopurinol use are needed and should be targeted towards high-risk groups, including older men and those receiving multiple concomitant medications.

Gout epidemiology: results from the UK General Practice Research Database, 1990-1999.

OBJECTIVE: To examine the epidemiology of gout and gout treatment in the United Kingdom using a large national practice based population. METHODS: Data from the UK General Practice Research Database from 1990 to 1999 were examined. Physician diagnoses and drug codes were used, and trends in gout incidence and treatment examined. Additionally, disease prevalence for the year 1999 was assessed. To examine the association of gout with comorbid disease, the prevalence of select health conditions and drug use was compared with the corresponding prevalences seen in osteoarthritis, adjusting for both age and sex. RESULTS: From 1 January 1990 to 31 December 1999 overall gout incidence remained relatively stable, ranging from a low of 11.9 cases (95% confidence interval (CI) 11.5 to 12.3) in 1991 to a high of 18.0 cases (95% CI 17.6 to 18.4) per 10 000 patient-years in 1994. Gout prevalence in 1999 was 1.4% with rates approaching 7% in men over the age of 65. Drugs used for the treatment of gout remained constant in prevalent cases with the exception of a significant decline in non-steroidal anti-inflammatory drug use over the 10 year follow up. Compared with patients with osteoarthritis, patients with gout were significantly more likely to have cardiovascular disease, hypertension, diabetes, and chronic renal failure, and were more likely to have used diuretics or ciclosporin, or both. CONCLUSION: Although gout is common in the UK, particularly among older men, the incidence of the disease seems to have remained stable during the 1990s.