Outcome Measures

Many of the earlier trials investigating interventions for non-specific LBP used different outcome measures which made between study comparisons rather problematic. It was then decided by a group of international investigators that a main set of 5 domains should be used in all trials to standardize the outcome measures and to better facilitate the comparability amongst studies (24). The five domains are (i) pain symptoms, (ii) back related function, (iii) Generic well-being, (iv) Disability and (v) Satisfaction with care. A brief description of the most common outcomes used within each of these domains is given below:

(i) Pain Symptoms

 Troublesomeness/Bothersomeness - this is typically a single question asking the patient how troublesome or bothersome their LBP is. Patients can answer the question by selecting one of the five possible response categories which are Not at all, Slightly, Moderately, Very much and Extremely (25, 26).

 Pain Severity – the severity or intensity of back pain is often measured using either a numerical rating scale (NRS) on a scale of 0 (No pain) to 10 (Worst possible pain) or a visual analogue scale (VAS) on a scale of 0 (No pain) to 100 (Worst imaginable pain) (27). The NRS is a one-dimensional measure that can be administered either graphically or verbally. The patient is required to indicate a whole number on an 11-point scale from 0 to 10 that best reflects their level of pain. The number indicated by the patient is then recorded by the person administering the questionnaire. The VAS on the other hand is a

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continuous one-dimensional scale that can take the form of either a horizontal or vertical line that is 100mm (10cm) in length. The VAS is administered to the patient for self-completion where the patient is required to draw a line

perpendicular to the VAS line that best reflects their level of pain.

 Frequency – this is a single question that enquires about how frequently the patient experiences LBP. The most commonly used question requires that the patient selects the category that best reflects their frequency of pain. The number of available response categories varies but the two extremes are usually ‘Never’ and ‘Always’. An alternative measure of frequency might be the number of days of pain over a certain duration e.g. over the past 4 weeks.

(ii) Back related function

 Roland Morris Disability Questionnaire (RMDQ) – the RMDQ questionnaire consists of twenty-four items and measures back related disability (28). The patient is required to tick any of the twenty-four items that applies to them. The final score is computed by simply counting the number of ticked boxes. The final score is on a scale of 0-24 where a lower score indicates less severe disability. However a problem with this questionnaire is that it has not got any ‘No’ tick boxes. This makes it impossible to distinguish whether an un-ticked box is genuinely un-ticked or has been missed by the patient.

 Oswestry Disability Index (ODI) – the ODI questionnaire consists of ten

questions related to everyday activities of daily living, where each question is on a scale of 0 (no disability) to 5 (worst disability) (29). The scores for each of the questions are then summed and converted to a scale of 0-100% where a lower score indicates less disability.

 Von Korff Scale (VKS) - the modified Von Korff questionnaire measures both pain and disability using six questions, with each question having a scale of 0

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(no pain/disability) to 10 (worst pain/disability). The first three questions are used to compute a measure of disability whereas the last three are used to measure pain. The scores are then transformed to a 0-100% scale where a lower score represents less pain or disability (30).

(iii) Generic well-being

 SF-12 or SF-36 - the SF-12 or SF-36 are commonly used as a measure of health- related quality of life. The SF-12 questionnaire consists of 7 questions with 12 items in total whereas the SF-36 questionnaire consists of 11 questions with 36 items in total (31, 32). An algorithm is then applied to the item responses to create eight subscales that measure functional health and well-being. These eight subscales measure physical functioning, role-physical, bodily pain, general health, vitality, social functioning, role-emotional and mental health. These eight subscales are then used to create two aggregated summary measures of physical and mental health. These are measured on a scale of 0- 100 where a lower score indicates poorer physical or mental functioning.

 EQ-5D – the EQ-5D is an outcome that measures the health-related quality of life of a patient. The questionnaire consists of two parts. The first part asks questions based on five dimensions (mobility, self-care, usual activities, pain/discomfort and anxiety/depression), hence why it is also referred to as the EQ-5D, where each dimension consists of three possible options (33). An algorithm is then applied to the responses to compute a healthy utility score that is usually on a scale of 0 (death) to 1 (perfect health state). It is also

possible to obtain a negative utility score which suggests that a patient’s quality of life is worse than death. The second part of the questionnaire consists of a visual analogue scale (VAS) that has a scale of 0 (worst imaginable health state)

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to 100 (best imaginable health state). The patient is required to mark on the scale how good or bad their health state is today.

(iv) Disability

 Days off work – this question simply asks the patient for the number of days off from work due to LBP over a certain period of time. The period of time for which this information is required varies from study to study e.g. number of days off from work during the past 4 weeks? Or number of days off from work during the past 3 months?

(v) Satisfaction

 Participant satisfaction – this is a single item question, as recommended by the international low back forum, that enquires about how satisfied the patient is with the effectiveness of the treatment they have received (24). There may be variations of the response categories available for this outcome measure. Typically the categorical responses are on a five point Likert scale ranging between the two extremes of ‘Very dissatisfied’ and ‘Very satisfied’.

 Specific health transition question – this single question asks the patient how they feel since they were last assessed. The patient can choose one of several categorical responses on a Likert scale that best reflects how they feel.

Responses include ‘are you much worse’, ‘a bit worse’, ‘the same’, ‘a bit better’ or ‘a lot better’.

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Table 2.1 – Comparison of interventions from high-quality RCTs at short term (3 month) and long term (12 month) follow-up

Mean Difference in RMDQ (95% CI); SMD

Study Control Intervention 3 month 12 month

UK BEAM (2004) GP care Exercise 1.36 (0.63, 2.10); 0.34 0.39 (-0.41, 1.19); 0.10 Manipulation 1.57 (0.82, 2.32); 0.39 1.01 (0.22, 1.81); 0.25 Manipulation plus exercise 1.87 (1.15, 2.60); 0.47 1.30 (0.54, 2.07); 0.33

ATEAM (2008) Usual care Massage 1.96 (0.74, 3.18); 0.39 0.58 (0.77, 1.94); 0.12 Alexander technique (6 sessions) 1.71 (0.47, 2.95); 0.34 1.40 (0.03, 2.77); 0.28 Alexander technique (12 sessions) 2.91 (1.66, 4.16); 0.58 3.40 (2.03, 4.76); 0.68

BeST (2010) Advice only Cognitive behavioural therapy 1.10 (0.38, 1.71); 0.22 1.30 (0.56, 2.06); 0.27

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