Monitoring in chronic disease: a rational approach

Introduction

“Know which abnormality you are going to follow during treatment. Pick something you can measure.”

Meador C. A Little Book of Doctors' Rules.Lyons: IARC Press, 1999

The ritual of routine visits for most chronic diseases usually includes monitoring to check on the progress or regress of the disease and the development of complications. Such checks require that we choose what to monitor, when to monitor, and how to adjust treatment. Poor choices in each can lead to poor control, poor use of time, and dangerous adjustments to treatment. For example, an audit of serum digoxin monitoring in a UK teaching hospital more than 20 years ago showed that the logic behind more than 80% of the tests requested could not be established, the timing of tests reflected poor understanding of the clinical pharmacokinetics, and about one result in four was followed by an inappropriate clinical decision.1 Improvements are possible. For example, a computerised reminder of inappropriate testing reduced the volume of testing for the concentration of antiepileptic drugs by 20%2; a decision support system for anticoagulation with warfarin led to an improvement from 45% to 63% of patients being within target range3; and quality control charts for peak flow measurements for people with asthma could detect exacerbations four days earlier than conventional methods.4 Given the extent of monitoring, even modest improvements are likely to improve benefits for patients and may reduce costs.

Monitoring is periodic measurement that guides the management of a chronic or recurrent condition. It can be done by clinicians, patients, or both. In Australia, monitoring comprises between a third and half of all tests ordered in general practice and outpatients (Pirozzo, personal communication, 2002). Despite the considerable staff time and resources involved, monitoring is a surprisingly understudied area. We review the current literature (based on a Medline search using the terms “monitor*“, …