Why is there no ±5% tolerance specified for the K-YBGL Beta-Glucan value?

The ± 5% tolerance applies to the experimental assay parameters, namely Total Glucan and Alpha-Glucan. These values are determined independently using the validated K-YBGL analytical procedure and are subject to the assay performance specifications and quality control criteria established for the method. Beta-Glucan is not measured directly. Instead, it is calculated from the difference between the two measured values:

Beta-Glucan = Total Glucan − Alpha-Glucan

As a result, the uncertainty associated with both the Total Glucan and Alpha-Glucan measurements contributes to the final Beta-Glucan result. When a value is calculated from two independent measurements, their uncertainties combine. This effect is particularly important when the Beta-Glucan concentration is relatively small compared to the Total Glucan and Alpha-Glucan values. In such cases, even small analytical variations in the measured values can lead to a proportionally larger variation in the calculated Beta-Glucan value. This is a normal and expected consequence of analytical error propagation and does not indicate an issue with assay performance.

Because Beta-Glucan is a calculated value rather than a directly measured parameter, assigning a fixed tolerance of ±5% would not accurately reflect the true experimental variability associated with the calculation. For this reason, the scientifically appropriate approach is to assign target values and acceptance criteria only to the directly measured parameters, Total Glucan and Alpha-Glucan. Customers should therefore verify assay performance using the Total Glucan and Alpha-Glucan target values provided with the control material and follow the acceptance criteria described in the product documentation. Successful recovery of these values demonstrates that the assay is performing as intended. The calculated Beta-Glucan result should be interpreted with the understanding that its variability may be greater than that of the directly measured parameters due to the combined uncertainty of the two underlying measurements.