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Use of randomised trials to decide when to monitor response to new treatment

BMJ 2008; 336 doi: (Published 14 February 2008) Cite this as: BMJ 2008;336:361
  1. Katy J L Bell, PhD candidate,
  2. Les Irwig, professor of epidemiology,
  3. Jonathan C Craig, professor of clinical epidemiology,
  4. Petra Macaskill, associate professor in biostatistics
  1. 1Screening and Test Evaluation Program, School of Public Health, Edward Ford Building (A27), The University of Sydney, NSW 2006, Australia
  1. Correspondence to: K J L Bell katyb{at}
  • Accepted 14 November 2007

Is monitoring initial response to treatment always helpful in clinical management of patients? Bell and colleagues have developed a framework for deciding whether surrogate outcomes should be used to monitor initial response to treatment in chronic disease.

Monitoring entails periodic measurement to guide management1 and is widely practised in clinical medicine to inform decisions throughout the course of a disease and to provide prognostic information to patients. It is helpful to divide monitoring into phases: pretreatment, initial response, maintenance, re-establish control, and post-treatment.1

Initial response monitoring uses repeat measurement soon after a new treatment is started to check that the response is within a range that maximises the benefits while minimising the harms. Table 1 summarises different types of initial response monitoring. We have limited our discussion to the use of surrogate outcomes for monitoring initial response to treatment. Surrogate outcomes are commonly used to monitor initial response in patients with chronic conditions. This type of initial response monitoring is common in clinical practice and can result in inappropriate decisions. We looked at two scenarios to develop a rational framework for deciding whether this form of initial monitoring should be done: Should change in blood pressure be monitored after addition of a diuretic to an angiotensin II receptor blocker in adults with essential hypertension? and Should change in cholesterol be monitored after giving patients with ischaemic heart disease a statin?

View this table:
Table 1

 Rationale for monitoring initial response to drug treatment

Rationale and pitfalls of monitoring initial response

Treatment for patients with chronic conditions (such as hypertension and raised cholesterol) is often monitored by using surrogate outcomes (such as blood pressure and cholesterol concentration). These outcomes are used to predict “hard” end points: the patient’s risk of a clinically important outcome (such as a stroke or myocardial infarction). These hard end points often occur many years after …

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