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 True screening opportunistic or anticipatory True screening What are the pros and cons of each?

Wilson’s Criteria Condition must be: Screening 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 Specificity 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: Doctors NHS 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