Credebo and Personal Equipoise
Two studies published online this week by Cook et al (Cook et al 2012) and Mannion et al (Mannion et al 2012) appear to highlight the importance of non-mechanical factors in patients’ response to treatment, namely credebo and personal equipoise.
Credebo is a term I came across on a Chartered Society of Physiotherapist forum discussion. One physiotherapist wrote that in order to have a placebo effect on a patient the therapist needed to be credible. This physiotherapist contended that clinically we had to earn the placebo effect and as such he termed it credebo.
Personal equipoise is an individual’s ability to approach a situation with no expectations, no bias. This is almost impossible for us to do as clinicians. We provide the patient with the most effective programme we can in order to provide ethical treatment. Therefore, we expect it to be the most effective option.
These two ideas come to light in these studies.
Mannion et al (2012) assessed the effect of core strengthening exercises on functional outcomes (Roland-Morris disability questionnaire) and low back pain intensity on a 0-10 scale. Interestingly, unlike many studies, they took the additional step of assessing core strength before and after the study period. Transversus abdominis (TrA), internal and external oblique activation were assessed using M-mode ultrasound with tissue Doppler imaging. Over the 9 weeks of therapy Roland-Morris score reduced from 8.9 to 6.7 on average and average pain from 4.7 to 3.5. Furthermore, the ability to voluntarily activate TrA improved by 4.5%. However, there was no improvement in activation of either oblique. There was a significant reduction in catastrophising. The authors of the study were keen to suggest the exercise programme its self may improve confidence and thus reduce catastrophising improving function and pain perception.
Some authors suggest that quite small percentage improvements in strength can have important functional benefits as in daily life the abdominals are rarely used above 40%. In addition, it is possible the method of assessment may not have been sensitive enough to pick up changes in activation. It is also possible the programme may have led to functional improvements not assessed in the study. Alternatively, the programme may be working through other mechanisms. Possibly strengthening other muscles not assessed, improved circulation to the lumbar spine increasing the rate of removal of inflammatory mediators or maybe through effects on improving the tensile strength of fascia.
Cook et al (2012) compared the effectiveness of early use of thrust and non-thrust manipulation in 149 subjects with low back pain. The average treatment period was 35 days. There was no difference at second visit or discharge in outcomes between groups in Oswestry disability index or numeric pain rating scale. However, they found that the personal equipoise of the therapist was directly correlated with the outcome of their patients. In other words the therapists expectations were directly correlated with the therapeutic result. As the Oswestry disability index and pain rating were self-report the therapists had no direct influence on the outcome measures.
The most likely mechanism for this effect is credebo. The therapist being so confident the patient responded favourably because their subconscious was convinced. The Mannion et al (2012) study may also have been affected by credebo. Undergoing a full treatment programme with a very clear and logical rationale whether it works or not will have a significant credebo affect.
How does this impact us clinically? Should we look to be as objective as possible and avoid having a credebo effect so that we can evaluate the mechanical effects of our treatments? Should we look to employ credebo and be as confident with clients as we can? Perhaps we should look to employ credebo as best we can and simultaneously take key objective markers not only of function but to assess the mechanical impact of our treatments?
I would love to know your thoughts!
Cook, C. Learman, K. Showalter, C. Kabbaz, V. O’Halloran, B., 2012. Early use of thrust manipulation: A randomized control trial. Manual therapy, Epub Oct 2nd.
Mannion AF, Caporaso F, Pulkovski N, Sprott H. 2012. Spine stabilisation exercises in the treatment of chronic low back pain: a good clinical outcome is not associated with improved abdominal muscle function. Eur Spine J. 21 (7), 1301-10.