For process of care, quality problems can arise in one of three ways: underuse, overuse, and misuse.
Underuse refers to the failure to provide a health care service when it would have produced a favorable outcome for a patient. Standard examples include failures to provide appropriate preventive services to eligible patients (e.g., Pap smears, flu shots for elderly patients, screening for hypertension) and proven medications for chronic illnesses (steroid inhalers for asthmatics; aspirin, beta-blockers, and lipid-lowering agents for patients who have suffered a recent myocardial infarction).
Overuse refers to providing a process of care in circumstances where the potential for harm exceeds the potential for benefit. Prescribing an antibiotic for a viral infection like a cold, for which antibiotics are ineffective, constitutes overuse. The potential for harm includes adverse reactions to the antibiotics and increases in antibiotic resistance among bacteria in the community. Overuse can also apply to diagnostic tests and surgical procedures.
Misuse occurs when an appropriate process of care has been selected but a preventable complication occurs and the patient does not receive the full potential benefit of the service. Avoidable complications of surgery or medication use are misuse problems. A patient who suffers a rash after receiving penicillin for strep throat, despite having a known allergy to that antibiotic, is an example of misuse. A patient who develops a pneumothorax after an inexperienced operator attempted to insert a subclavian line would represent another example of misuse.