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The effect of correlations between screening markers on screening performance.
1Wolfson Institute of Preventive Medicine, Barts and the London Queen Mary's School of Medicine and Dentistry, Charterhouse Square, London EC1M 6BQ, UK. j.k.morris@qmul.ac.uk
Journal of Medical Screening
|October 11, 2007
Summary
Correlations between screening markers can impact screening performance. Positive correlations may decrease performance, while negative correlations can increase it, depending on marker characteristics. Effects are typically modest in real-world scenarios.
Area of Science:
- Biostatistics
- Medical Screening
Background:
- The impact of correlations between multiple screening markers on overall screening performance is not fully understood.
- It is commonly assumed that marker correlations generally degrade screening effectiveness.
Purpose of the Study:
- To quantitatively investigate the effect of correlations between two screening markers on screening performance.
- To use prenatal screening for Down's syndrome as a specific example, with generalizable results.
Main Methods:
- Monte Carlo simulation was employed to generate data for two hypothetical markers, A and B.
- Simulations included 1000 affected and 1000 unaffected pregnancies, with variations in marker means, standard deviations, and correlations.
Main Results:
- When markers are higher on average in affected pregnancies, positive correlations decrease performance, and negative correlations increase it.
- When one marker is higher and the other lower in affected pregnancies, positive correlations increase performance, and negative correlations decrease it.
- Strong correlations (r > 0.45 or < -0.45) significantly impact performance, while modest correlations have minimal effect when individual marker performances differ.
Conclusions:
- Marker correlations can either enhance or diminish screening performance.
- These effects are generally modest in practice due to typically weak correlations between markers.
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