Musculoskeletal problems are painful and disabling and can cause poor health; such individuals are often referred to physiotherapy for treatment . Access to physiotherapy in the UK NHS has traditionally been associated with long waiting times for an initial consultation, with delays of up to several months . Consequently, many patients fail to attend their consultation or the consultation provides little benefit as patients are seen too late . In response to waiting list pressures, new physiotherapy-led telephone assessment and treatment services known as PhysioDirect have been developed and are available in some areas of the UK . The MRC PhysioDirect trial was a multi-centre pragmatic equivalence RCT designed to test the clinical and cost-effectiveness of PhysioDirect services. Patients were randomised in a 2:1 ratio to PhysioDirect or usual physiotherapy care where patients were placed onto waiting lists and waited for the next available appointment . The trial incorporated a run-in period of consolidation of between seven and twelve weeks varying between the participating primary care trusts (PCTs) prior to the main trial. The data from this trial will be used for the purposes of this paper.
Multisite research ethics approval for the PhysioDirect trial was obtained from Southmead research ethics committee, reference 08/H0102/95. All participants gave informed written consent.
In the PhysioDirect trial, in the PhysioDirect service, patients wishing to access physiotherapy treatment could telephone a senior physiotherapist for an initial assessment followed by appropriate advice over the telephone supplemented by leaflets through the post. Physiotherapists used bespoke software to provide a template for their assessment and as an electronic medical record of the consultation. Patients were invited to telephone the service two to four weeks later to report progress. Patients were invited to a face to face consultation if they needed urgent care or if their condition failed to improve.
A new PhysioDirect service was set up in four PCTs. As PhysioDirect was a new service, eight physiotherapists from each PCT (32 in total) undertook a structured training programme and had to be certified as competent to deliver the service, however it was expected the physiotherapists would require a period of practice and consolidation before they became familiar with delivering the new service. To ensure the PhysioDirect service was running efficiently prior to its formal evaluation in the main RCT, the PhysioDirect trial operated in two phases. The first phase was a run-in period of consolidation which lasted 12, 10, 11 and 7 weeks for PCTs A, B, C and D respectively. Patients recruited during this phase were randomised to either the usual care arm or to the PhysioDirect arm. The second phase was the main trial which recruited and randomised a fresh set of patients to the two arms. Patients randomised in the run-in period were not included in the main trial analysis, thus creating two separate datasets for analysis in this study. The run-in period allowed physiotherapists to build their confidence and competence in delivering the PhysioDirect service and to embed key processes. In particular, it was anticipated that the length of telephone calls would decrease as the physiotherapists gained confidence in consulting with patients by telephone and in using the PhysioDirect software.
By comparing the data collected from the run-in period with those from the main trial, we examined two issues. First, whether the length of telephone consultations changed over time, as this could have important implications for the cost-effectiveness of the PhysioDirect service. Second, whether patients’ clinical outcomes differed between those who were recruited in the run-in period and main trial.
Key outcomes for this study include both process and clinical outcomes. The key process outcome was the length of the telephone call in the PhysioDirect service. The date and call time of each telephone call made by a patient to the PhysioDirect service and the physiotherapist who handled the call was recorded. Only the participant’s initial call was used in the analysis as follow up call times were shorter as patient details were already known.
Two key clinical outcomes were used for the purposes of this study. The first was the primary clinical outcome for the trial, the physical component score (PCS), from the SF-36v2 patient reported questionnaire of general health. PCS is a generic measure of physical function which is scored from 0 to 100 with lower scores indicating worse physical function . The second was the Measure Yourself Medical Outcome Profile v2 (MYMOP2), which is a patient generated score. Patients specified their symptoms and limitations for which they were referred to physiotherapy. The follow-up questionnaire was tailored to the patient’s specified symptoms and limitations in order to assess change in those symptoms and limitations . These clinical outcomes were measured at baseline before randomisation and six months later for patients in both the run-in period and main trial.
Key process measure - telephone call time
It was envisaged that mean call time would initially be high during the run-in period but would gradually decrease as the physiotherapists grew in confidence and competence in using the new service. Call time was expected to stabilise at around 20 minutes based on the experience of the team responsible for training physiotherapists in the PhysioDirect service .
To investigate if, and when, call time had reached a plateau, descriptive statistics compared mean call time between the two phases. The two phases of the trial can be viewed on one timeline as the main trial commenced recruitment immediately after the run-in period thus allowing the call time trend to be explored. The timeline was defined from the date the first patient was referred to physiotherapy and screened for eligibility for the trial in the run-in period to the date that the last patient was referred to physiotherapy in the main trial. Participating PCTs’ timelines were not comparable as each PCT commenced recruitment at different times in the year. Therefore within each PCT, patients were grouped into weeks according to the date of their referral to physiotherapy from the start of the run-in period. A four week rolling mean call time plot illustrated whether there was a trend in call times as patients were recruited to the trial.
Modelling call time trend needs to detect changes in gradient as it was expected physiotherapists’ call times would shorten over time. Joinpoint regression analysis detects these change points (known as a joinpoint) and determines the gradient between joinpoints . Using the timeline described above assumes all physiotherapists had delivered the PhysioDirect service at approximately the same time (that is the start of the run-in period) and had taken the same number of calls per week therefore a different timeline was used. For each physiotherapist, the call times of all their telephone calls were ordered from the earliest date and time of the call. Mean call times were calculated across the physiotherapists in order to represent the mean duration of their first call, second call, third call, and so on. Specifying a maximum of three joinpoints to be used in the modelling, three permutation tests using Monte Carlo methods determined the optimal number of joinpoints needed to describe the mean call time trend: i) testing the null hypothesis of zero joinpoints against the alternative of three joinpoints, ii) testing one joinpoint against three joinpoints, iii) testing two jointpoints against three jointpoints . If no joinpoints were identified, this would suggest the trend had no significant changes of direction; if joinpoints were identified this would suggest there were significant changes in direction which may correspond to when call time had reached a plateau. To determine how long it had taken physiotherapists’ call time to plateau, call times were plotted against the week the patient was referred to physiotherapy, thus identifying when call time had stabilised.
Multilevel models  were used to model call time taking into account the clustering effects from the physiotherapists and PCTs; the call times within each physiotherapist were ordered from the earliest date and time of the call. The variance partition coefficient (VPC) was calculated from the null model, which is no adjustment for explanatory variables. This would establish whether the variability in call times was attributable at the PCT level or between physiotherapists within a PCT .
Key clinical outcomes - physical function and symptom change
To investigate whether patients’ clinical outcomes for those recruited in the run-in period differed to those recruited in the main trial, summary statistics for physical function (SF-36v2 PCS) and symptoms (MYMOP2) at baseline and six months were described for both phases. For each patient, their change in clinical outcome at six months was calculated by subtracting their baseline score from their six month score. A positive change in physical function or a negative change in symptoms indicates improvement in health at six months. Viewing the two phases of the trial on one timeline, a four week rolling mean plot for patients’ change in clinical outcomes at six months showed whether patients recruited in the run-in period had greater or smaller changes in clinical outcomes compared to patients recruited in the main trial.
An analysis of covariance (ANCOVA) compared mean physical function at six months between the PhysioDirect service and usual care (that is the treatment effect) adjusting for baseline physical function, age, gender, PCT and referral problem in the run-in period and the main trial. The clinical effectiveness of the PhysioDirect service and usual care were deemed equivalent if the 95% confidence interval from its treatment effect lay between -2 and 2 points on the physical function scale . An independent t-test compared the treatment effect from the run-in period to the main trial . The ANCOVA was repeated for symptoms at six months and replacing baseline physical function with baseline symptoms, followed by the independent t-test. For the symptoms scale, a difference of no more than 0.5 points was defined as demonstrating equivalence .
Longitudinal modelling  was used to model the dynamics of the clinical outcomes at six months for usual care and PhysioDirect over time where time is week of referral to physiotherapy. This would illustrate that patient clinical outcomes did not differ between patients recruited within the same phase or between different phases of the trial. The modelling adjusted for week of patient referral, treatment and phase of the trial plus a three way interaction term.
Joinpoint Regression Programme v4.0.1.  was used for the joinpoint regression modelling and all other analyses were conducted in STATA v12 .