Use of a structured intervention can double the rate of chlamydia screening in practices, a UK study has found.

A prospective, cluster randomised controlled trial tested whether using the components of the theory of planned behaviour (TPB) improved chlamydia screening rates in general practices.

The TPB postulates that intention of a behaviour (in this case offering screening for chlamydia to at-risk groups) is dependent on three factors: personal attitude (e.g. awareness of benefits of testing and prevention of long-term complications); subjective norms (the extent to which this is expected or normal behaviour); and perceived behaviour control (whether the person feels able to offer the test or if there are any facilitating factors or barriers).

Practices were recruited from 11 primary care trusts (PCTs) in SW England from 2009 to 2011. They were not told they were participating in a trial but consent was obtained by PCT and public health leads; this Zelen design overcomes potential bias from participants modifying their behaviour because they know they are in a trial.

All intervention practices were offered a workshop based on the TPB for all staff, delivered by a Health Protection Agency researcher (called a generic chlamydia support worker to avoid unblinding). Presentations on epidemiology and benefits of diagnosis and treatment were aimed to change personal attitudes to chlamydia screening; videos and a script were used to overcome lack of confidence to offer screening; posters and patient invitation cards to address subjective norms; and computer reminders to influence behavioural controls.

The chlamydia support worker helped staff adapt the intervention to individual practices, identified a local chlamydia champion and offered two further contacts in the nine month follow-up. The control practices just received a screening information pack and area-specific training. Both control and intervention practices continued to receive usual support from their local chlamydia screening coordinator; involving telephone contact or visits as well as partner notification.

Data were available for 76 intervention and 81 control practices. Overall, 62% of practices agreed to three contacts with the chlamydia support worker; 21% one or two and 17% refused all contacts.

Testing rates from the 47 practices that fully engaged with interventions increased by 2.33 times compared with controls, rate ratio (RR) 2.33 (95% CI:1.63-3.34, P < 0.001); absolute rates were: 5.55 per 100 patients aged 15-24 years in intervention practices, 2.85 in controls and 2.22 in non-engaged practices.

The higher testing rates in intervention practices remained in the post-intervention period, RR 1.97 (95% CI:1.40-2.77); absolute rates were: 4.20 per 100 patients in the intervention group, 2.45 in controls and 1.32 in non-engaged practices.

The number of chlamydia infections diagnosed in fully engaged practices was 1.8 times greater than in controls (95% CI:1.2-2.5, P = 0.005); the absolute rates of positive diagnoses were: 3.2 per 1,000 patients in fully engaged practices, 2.2 in controls and 1.0 in non-engaged practices. This persisted nine months later when intervention practices had 1.6 times greater numbers than controls

(95% CI: 1.1-2.4, P = 0.03); absolute numbers of chlamydia diagnoses were: 2.7 per 1,000 patients aged 15-24 in intervention practices, 1.7 in both controls and non-engaged practices.

When testing rates were calculated using intention to treat analysis, the benefits were more modest: absolute testing rates across all intervention practices increased from 2.43 to 4.34 per 100 15-24 year olds; control practices increased from 2.61 to 3.00; unadjusted RR 1.66 (95% CI: 1.1-2.5). After adjustment for age, sex, PCT, month and deprivation, the rate in intervention practices was 1.76 times as great as control practices

(95% CI: 1.24-2.48, P < 0.001). This difference persisted throughout the nine-month follow-up: estimated RR 1.57 (95% CI: 1.07-2.30, P = 0.02; absolute testing rate in the intervention arm 3.46, controls 2.82 per 100 15-24 year olds.

The authors concluded that this complex intervention doubled chlamydia screening in the practices that fully engaged with the programme; although when all those that did not fully participate were included, as in a real-life situation, this rate ratio was more modest.

Behaviour change strategies to encourage primary care teams to increase chlamydia testing does have some modest outcomes and therefore merits. It is encouraging to see that financial incentives are not the panacea to changing behaviour of primary healthcare teams to improve public health outcomes.

Dr Richard Ma