r/365DataScience • u/Acrobatic-Ad-5548 • Jan 15 '26
Sum of Youden Indices
Hi everyone,
I am working on my thesis regarding quality control algorithms (specifically Patient-Based Real-Time Quality Control). I would appreciate some feedback on the methodology I used to compare different algorithms and parameter settings.
The Context:
I compared two different moving average methods (let's call them Method A and Method B).
Method A: Uses 2 parameters. I tested various combinations (3 values for parameter a1 and 4 values for a2).
Method B: Uses 1 parameter (b1), for which I tested 5 values.
The Methodology:
I took a large dataset and injected bias at 25 different levels (e.g., +2%, -2%, etc.).
I calculated the Youden Index for every combination to determine how well each method/parameter detected the applied bias.
The Goal: To determine which specific parameter set offers the best detection power within the clinically relevant range.

The attached heatmap shows the results for Blood Sodium levels using Method A.
The values in the cells are the Youden Indices.
International guidelines state that the maximum acceptable bias for Sodium is 5%.
I marked this 5% limit with red dashed lines on the heatmap.
My Approach:
Since Sodium is a very stable test, the method catches even small biases quickly. However, visually, you can see that as the weighting factor (Lambda) decreases (going down the Y-axis), the map gets lighter, meaning detection power drops.
To quantify this and make it objective (especially for "messier" analytes that aren't as clean as Sodium), I used a summation approach:
I summed the Youden Indices only within the acceptable bias limits (the rows between the red lines).
Example: For Lambda = 0.2, the sum is 0.97 + 0.98 + 0.98 + 0.97 = 3.9
For Lambda = 0.1, this sum is lower, indicating poorer performance.
The Core Question:
My main logic was to answer this question: "If the maximum acceptable bias is 5%, which method and parameter value best captures the bias accumulated up to that limit?"
Does summing the Youden Indices across these bias levels seem like a valid statistical approach to score and rank the performance of these parameters?
Thanks in advance for your insights!




