Screening and Prevention

Prevention

• Can be classified into three types:

• Primary

• Secondary

• Tertiary

Primary Prevention

• Removing the cause

• Sanitation

• Passive smoking

Secondary Prevention

• Identify presymptomatic disease before damage is done

• Examples?

• Blood pressure

• Diabetic screening

Tertiary Prevention

• Limiting complications and disability in established disease by regular surveillance

• Examples?

• Diabetic Retinopathy Screening

Methods of Screening

• Case Finding– opportunistic or anticipatory

• True screening

• What are the pros and cons of each?

Wilson’s Criteria

• Condition must be: – common– important– diagnosable– have a latent interval

• Screening must be:– cheap and simple– continuous– targeted towards a high risk group

Wilson’s Criteria

• Although the following were not part of Wilson’s original criteria we might add:– Disease readily treatable– Tests sensitive, specific, safe, acceptable and

easy to interpret– Benefits outweigh costs

The Test

• Explain the following terms:– Sensitivity

• few false negatives

– Specificity• few false positives

– Positive Predictive Value• likely to be correct when positive

The Test

• Discuss the trade off between sensitivity and specificity

• What happens if the prevalence is low?– even test of high sensitivity and specificity have

a low predictive value

• Do we move the point of death?

• Imperfect knowledge of natural history of the condition causes what problems?

Benefits of Screening

• Improved mortality

• Improved morbidity

• Possible savings on costs of future treatment

Costs of Screening

• Patients:– anxiety– false reassurance– economic

• Doctors

• NHS

Obstacles to Prevention

• Discuss the obstacles to prevention from:– patients– doctors– NHS

Overcoming Patient Obstacles

• Point out debits

• Point out benefits

• Anticipate and discuss difficulties

• Suggest coping stategies

• Simple advice and written information