Email updates

Keep up to date with the latest news and content from BMC Medical Research Methodology and BioMed Central.

Open Access Research article

The index ‘Treatment Duration Control’ for enabling randomized controlled trials with variation in duration of treatment of chronic pain patients

Hilbert W van der Glas* and Robert J van Grootel

Author Affiliations

Department of Otorhinolaryngology and Head & Neck Surgery, University Medical Center Utrecht, G05.129, P.O. Box 85500, 3508 GA, Utrecht, The Netherlands

For all author emails, please log on.

BMC Medical Research Methodology 2013, 13:123  doi:10.1186/1471-2288-13-123

Published: 11 October 2013



Treatment duration varies with the type of therapy and a patient’s recovery speed. Including such a variation in randomized controlled trials (RCTs) enables comparison of the actual therapeutic potential of different therapies in clinical care. An index, Treatment Duration Control (TDC) of outcome scores was developed to help decide when to end treatment and also to determine treatment outcome by a blinded assessor. In contrast to traditional Routine Outcome Monitoring which considers raw score changes, TDC uses relative change.


Our theory shows that if a patient with the largest baseline scores in a sample requires a relative decrease by treatment factor T to reach a zone of low score values (functional status), any patient with smaller baselines will attain functional status with T. Furthermore, the end score values are proportional to the baseline. These characteristics concur with findings from the literature that a patient’s assessment of ‘much improved’ following treatment (related to attaining functional status) is associated with a particular relative decrease in pain intensity yielding a final pain intensity that is proportional to the baseline. Regarding the TDC-procedure: those patient’s scores that were related to pronounced signs and symptoms, were selected for adaptive testing (reference scores). A Contrast-value was determined for each reference score between its reference level and a subsequent level, and averaging all Contrast-values yielded TDC. A cut-off point related to factor T for attaining functional status, was the TDC-criterion to end a patient’s treatment as being successful. The use of TDC has been illustrated in RCT data from 118 chronic pain patients with myogenous Temporomandibular Disorders, and the TDC-criterion was validated.


The TDC-criterion of successful/unsuccessful treatment approximated the cut-off separating two patient subgroups in a bimodal post-treatment distribution of TDC-values. Pain intensity decreased to residual levels and Health-Related Quality of Life (HRQoL) increased to normal levels, following successful treatment according to TDC. The post-treatment TDC-values were independent from the baseline values of pain intensity or HRQoL, and thus independent from the patient’s baseline severity of myogenous Temporomandibular Disorders.


TDC enables RCTs that have a variable therapy- and patient-specific duration.

Randomized trial methodology; Decision rules; Routine outcome monitoring; Treatment duration; Chronic pain; Temporomandibular disorders; Quality of life; EQ-5D