Disease Screening Application Using Shiny

• Suppose you take a diagnostic screening test for a particular condition or disease.

• You test is postive. What is the probability you have the disease?

• You test is negative. What is the probability you have the disease?

• This Shiny application answers these questions.

User Inputs

• Prevalence: Percent of the population that has the disease

• Sensitivity: Detection rate of people with disease. Also called the True Positive Rate.

• Specificity: Detection rate of people without the disease. Also called the True Negative Rate

Outputs

• Postive Predictive Value (PPV): Given you a positive test result, the probability that you actually have the disease.

• False Omission Rate (FOR): Given a negative test results, the probability that you actually have the disease.

# Inputs
Prevalence  <- 0.09    
Sensitivity <- 0.41
Specificity <- 0.93

# Calculations & Outputs
print(PPV <- (Sensitivity * Prevalence) / ((Sensitivity * Prevalence + 
         (1 - Specificity)*(1 - Prevalence))))

[1] 0.3667992

print(FOR <- 1 - (Specificity * (1 - Prevalence)) / ((1- Sensitivity) * Prevalence + 
         (Specificity*(1 - Prevalence))))

[1] 0.05903936