This professional Excel tool allows medical laboratories to calculate Measurement Uncertainty (MU) in full alignment with ISO 15189:2022 and ISO/TS 20914:2019.
All calculations are automated and protected, requiring only minimal user input.

The workbook includes separate sheets for Chemistry, Immunology, and Haematology, using a standardised structure for easy comparison across departments.

The tool calculates all components required for ISO-compliant MU reporting:

1. Long-term imprecision (CV%)

Calculated from internal quality control (IQC) results.
You enter the Mean and Standard Deviation (SD), and the file calculates:

CV% = (SD / Mean) * 100

2. Bias (%)

Based on comparison between the laboratory result and the assigned value from external quality control (EQA).

Bias% = (Laboratory_Value - Reference_Value) / Reference_Value * 100

This is then used in the uncertainty calculations.

3. Bias uncertainty (Ubias%)

ISO/TS 20914 uses the standard uncertainty of bias as:

Ubias% = Bias% / SQRT(3)

4. Calibrator uncertainty (Ucalibrator%)

Entered by the user from the manufacturer’s insert.
The value is used directly in the combined uncertainty.

5. Pipette uncertainty (Upipette%)

Entered by the user based on pipette specifications or validation.

6. Combined uncertainty (Uc%)

Calculated automatically using the ISO/TS 20914 formula:

Uc% = SQRT( (CV%)^2 + (Ubias%)^2 + (Ucalibrator%)^2 + (Upipette%)^2 )

This represents the overall combined uncertainty of the measurement system.

7. Expanded measurement uncertainty (Ue%)

Using a coverage factor k = 2 (95% confidence), the expanded uncertainty becomes:

Ue% = Uc% * 2

This is the value required for ISO 15189 reporting.

8. Expanded uncertainty in measurement units (Ue)

For direct clinical interpretation, the uncertainty is also expressed in the analyte's unit of measure:

Ue = (Ue% / 100) * Mean

This value is suitable for accreditation reports, method validation, and quality documentation.

How the file works:

✔️ You enter:

• Mean (from IQC)

• SD (from IQC)

• Xi (your lab’s value from EQA)

• Xref (assigned value from EQA)

• Ucalibrator%

• Upipette%

✔️ The file automatically calculates:

• CV%

• Bias and Bias%

• Ubias%

• Combined uncertainty (Uc%)

• Expanded uncertainty (Ue% and Ue)

✔️ All formulas are locked and protected
✔️ Only editable fields are highlighted for the user
✔️ No calculations can be accidentally changed

📘 References Used

This calculator strictly follows the methodology described in:

• ISO 15189:2022 – Medical laboratories – Requirements for quality and competence

• ISO/TS 20914:2019 – Practical guidance for the estimation of measurement uncertainty

• CLSI EP15-A3 – Precision verification

• CLSI EP29-A – Measurement uncertainty documentation

All formulas used are consistent with international requirements for MU reporting.

🎯 Who Should Use This Tool

• ISO 15189 accredited laboratories

• Laboratories preparing for accreditation

• Chemistry / Immunology / Haematology departments

• QC managers and quality officers

• Medical laboratory specialists and biochemists

• Private laboratory networks standardising MU calculations

Why is it useful?

Most laboratories struggle with:

• Time-consuming calculations

• Inconsistent methods

• Missing components

• Manual Excel errors

• Preparing for external audits

This tool provides a ready-to-use, standardised, ISO-compliant solution, saving hours of work while ensuring accuracy and traceability.

Disclaimer: This Excel tool supports internal quality calculations in medical laboratories but does not replace professional judgement, accreditation requirements, or official regulatory documents. The user is responsible for verifying all results and ensuring compliance with local regulations and ISO 15189 standards.