Outcome assessment

Illustrative example - WHO pre-eclampsia trial

Outcome variables are classified as primary or secondary.  The primary outcomes of the study are selected on the bases of the following: they can be affected by the intervention, represent an important clinical outcome, are recorded routinely by treatment blinded observer and occur frequently to provide sufficient statistical power.  The primary maternal outcome of the trial is pre-eclampsia.

Hypertension is defined as blood pressure greater than or equal to 140mmHg systolic and/or 90mmHg diastolic occurring in two occasions at least four hours to a week apart after the 20th week of pregnancy.  Diastolic blood pressure will be measured at 5th Korotkoff sound, which is the disappearance of the sounds.  Proteinuria is defined if protein in urine is ≥ 300mg in 24 hours urine specimen or corresponding level of 2+ or more on dipstick.  Pre-eclampsia is defined as hypertension associated with proteinuria.    

Maternal secondary outcomes are: early onset pre-eclampsia (pre-eclampsia starting before 32 weeks of gestation), pregnancy induced hypertension (PIH), eclampsia and placental abruption. (WHO Multicentre Randomized Trial of Calcium Supplementation for the Prevention of Pre-eclampsia - go to protocol)

Illustrative example - CRASH trial

The primary outcome measures are:

• Death from any cause within two weeks of injury

• Death or dependence at six months

Long term recovery will be assessed at six months using the Glasgow Outcome Scale (GOS) which assesses disability and handicap in major areas of life.  The GOS will be administered by a postal questionnaire, completed by a patient or carer, or by telephone interviews.  (CRASH Trial - go to protocol)

Illustrative example - RaPP trial

We have chosen three main outcome measures, reflecting the elements of clinical practice targeted by our intervention [educational outreach visit with audit and feedback, and computerised reminders]:

• Proportion of prescriptions of other antihypertensives than thiazides to patients who are being prescribed antihypertensive drugs for the first time (Measurement: data drawn from the practice computer-system).

• The proportion of patients where the level of cardiovascular risk has not been estimated among all those started on antihypertensive or cholesterol lowering treatment (versus a sample not put on treatment). (Method: Physicians are given the names of the patients they have put on treatment and are asked if the cardiovascular risk has been evaluated, and if so: what the level was).

• Proportion of patients with a recorded level of cholesterol (total or LDL) or hypertension not satisfying the specified treatment goals, among all patients on the corresponding treatment. For cholesterol we have decided to also include patients on secondary prevention therapy since the treatment goals are similar (Measurement: data drawn from the practice computer system).

We will also investigate the following outcomes:

• The proportion of patients reporting that they were not involved in the decision-making process before drug treatment for hypertension and/or elevated cholesterol was started. (Measurement: questionnaire to patients started on treatment).

Economic analysis

We will record parameters that describe costs related to our intervention:

• Salary-costs

• Time spent arranging for appointments at the doctors’ practices

• Travel expenses in connection with each outreach visit

• Amount of physician-time spent at each visit

• Materials

• Training

• Other direct expenses related to the implementation of the intervention

(RaPP Trial - go to protocol)