The impact of (some) patient and site factors on assay sensitivity Robert H. Dworkin, PhD Professor of Anesthesiology, Neurology, Oncology, and Psychiatry
Dec 13, 2015
The impact of (some)
patient and site factors
on assay sensitivity
Robert H. Dworkin, PhD
Professor of Anesthesiology, Neurology, Oncology, and Psychiatry
Professor, Center for Human Experimental Therapeutics
University of Rochester School of Medicine and Dentistry
Patient factors Considerations for improving assay sensitivity
Pain duration: minimum
Pain duration: maximum
Baseline pain intensity: minimum
Baseline pain intensity: maximum
Baseline pain variability
Baseline pain consistency
Baseline diary compliance
Prior treatment failure
Psychopathology
Subject training
Study design factors Considerations for improving assay sensitivity
Research design
Number of treatment groups
Active comparator
Initial dose titration period
Flexible vs. fixed dosing
Rescue medication
Concomitant analgesics
Baseline period duration
Study duration
Study site factors Considerations for improving assay sensitivity
Number of sites
Staff training
Staff-patient interactions
Geographic location
Patient referral sources
Accelerated enrollment
Protocol concealment
Infrastructure
J Clin Psychopharmacol 2007;27:1-5
Effect size as a function of interview quality:HAM-D ratings in major depressive disorder RCTs
mean difference vs pbo SES p
Study 11
all raters 0.5 0.46* 0.61high quality 6.8 1.33 0.02
Study 22
all raters 2.14 0.20high quality 5.99 0.01
*standardized effect size of SSRIs from meta-analysis.
1Kobak KA, et al. Interview quality and signal detection in clinical trials. Am J Psychiatry 2005;162:628.
2Cogger KO. Rating rater improvement: a method for estimating increased effect size and reduction of clinical trial costs. J Clin Psychopharm 2007;27:418-420.
Select the number that best describes your neuropathic pain during the past 24 hours. (Circle one number only)
0 1 2 3 4 5 6 7 8 9 10
Nopain
Worst possible pain
Primary efficacy endpoint:
daily pain diary
Patient factors Study design factors Study site factors
Baseline pain intensity: minimum
Baseline period duration Staff training
Baseline pain intensity: maximum
Staff patient interactions
Baseline pain variability
Protocol concealment
Baseline pain consistency
Baseline diary compliance
Subject training
Can baseline pain diaries be used to
identify patients who will provide
increased assay sensitivity?
“Individuals with a greater pain variability index at baseline were more likely to be responders ... to placebo ... suggesting that a high pain variability may be a predictor of a placebo response.”
Harris RE, et al. Arthritis Rheum 2005;52:3670-3674.
“Because of the larger placebo response for pain-related endpoints … in the high variability patients, the apparent treatment effect size of MLN was smaller in patients with higher pain variability.”
Palmer RH, et al. International Conference on Accelerating the Development of Enhanced Pain Treatments, Bermuda, March 2011.
“In duloxetine studies for 3 chronic pain conditions (DPNP, CLBP, OA), patients with higher baseline pain variation had a smaller effect size and/or lower treatment response (relative to placebo) compared with patients with lower baseline pain variation.
Zhang S, et al. International Conference on Accelerating the Development of Enhanced Pain Treatments, Bermuda, March 2011.
Selecting subjects based on
characteristics of their baseline pain
ratings that might reflect rating
“diligence” or “competence” is likely to
be less efficient than providing training
before the baseline so that fewer
subjects will be excluded because of
their baseline ratings.
Patient selection
Patient training
Patient training:
1. Educating the patient that it is very important that pain ratings be made in a conscientious and thoughtful manner because this is necessary for the study to succeed in determining whether or not the treatment is effective.
2. Identification of personal anchors and use of reminders for rating pain in a consistent manner throughout the study.
3. Educational scripts and interviews specifically designed to manage patient expectations.
“Though it is natural to hope for a positive outcome during the trial, we want you to be aware that there is a good likelihood that you are on placebo during this trial.
Though you are likely to appreciate the care that you get from the study staff in this trial, it is very important that you don’t tell us that you are better if you’re really not, just because you are appreciative of the study staff, and you feel that you will be letting them down if you don’t improve.
We need you to report your condition as accurately as you possibly can...”
—D.L. Zimbroff, 2001
“Both investigators and patients were
blinded to the following information: entry
criteria for patients’ pain intensity, baseline
pain intensity, definition of responder
groups, visit at which randomization
occurred, treatment during the withdrawal
phase, efficacy failure criteria, and
computation rules and time windows in the
IVRS system used to calculate the baseline
intensity and pain response.”
Hewitt DJ, et al. Pain 2011;152:514-521.
Baseline score inflation in psychiatry
“The HAM-D ratings completed by the on-site evaluator were significantly higher than the centralized raters’ scores at screening and baseline, but not at endpoint.
At screening, 36% of patients who were judged to be eligible for the study by the on-site evaluator (ie, they scored at least 17 on the HAM-D, the study’s minimum severity criterion) were rated as study ineligible by a centralized rater….
…lower baseline scores are associated with greater change with placebo.”
Patient education:
1. Missing data diminishes the scientific value of the study and of the other subjects’ participation.
2. Emphasize importance of outcome assessments even if subject decides to discontinue study treatment and visits, although consent can, of course, be withdrawn at any time.
Internal validity vs. external validity(i.e., generalizability)