Evidence-Based Medicine (EBM)

“Positive predictive value refers to the percentage of patients with a positive test for a disease who actually have the disease. The negative predictive value of a test is the proportion of patients with negative test results who do not have the disorder.

The percentage of patients with a disorder who have a positive test for that disorder is a test’s sensitivity. The percentage of patients without a disorder who have a negative test for that disorder is a test’s specificity.”

BIOSTATISTICS

• Evidence-Based Medicine (EBM)
• Sensitivity (Sn)
• Specificity (Sp)
• Positive Predictive Value (PPV)
• Negative Predictive Value (NPV)
• Risk difference and Attributable Risk
• Relative risk
• Odds ratio
• Likelihood Ratio
• Anchoring bias
• TYPES OF STUDIES IN EPIDEMIOLOGY

 

The AFP EBM Glossary.

The ideal confirmation test will have both high sensitivity and high specificity.

Having a positive or negative test isn’t final. A positive or negative predictive value predicts the likelihood that your test result is actually true.

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Note: Risk=Probability

Attributable risk:

Standard deviation:

Skewed distribution:

Test reliability:

Test validity:

Correlation Coefficient:

Confidence Interval:

Comparison of data

1. “Chi-squared test: Used to compare percentages or proportions (nonnumerical or nominal data)
2. T-test: Used to compare two means
3. Analysis of variance (ANOVA): Used to compare three or more means.” From Crush Step 3

 

Incidence: (New cases of a disease) ÷ ( population at risk) in a given period of time

Prevalence: (Total cases of disease) ÷ ( population). It can be at a single point in time (“ point prevalence”) or over a period of time (“ period prevalence”)

The number needed to treat/ harm: # of pts that must be treated to prevent/ cause 1 pt to have the measured outcome; 1/( risk difference), e.g., 1/( 0.1) → NNT of 10

TYPES OF STUDIES IN EPIDEMIOLOGY

Types of studies in epidemiology.

References:

• Leon Gordis, Epidemiology, 5th Edition.
• Pocket Primary Care
• Adam Brochert, Crush Step 3
• http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1706071/
• http://www.aafp.org/fpm/2004/0500/p47.html (A Simple Method for Evaluating the Clinical Literature)
• https://onlinecourses.science.psu.edu/stat507/node/71 (Sensitivity, Specificity, Positive Predictive Value, and Negative Predictive Value)
• http://handbook.cochrane.org/chapter_9/9_2_2_4_measure_of_absolute_effect_the_risk_difference.htm
• http://childhoodcancer.cochrane.org/non-randomised-controlled-study-nrs-designs
• Goldman L, Schafer AI (eds): Goldman’s Cecil Medicine, ed 25. Elsevier Saunders, 2016, pp 37-41.