Request for: New Units of Measure to be used by NSWHP

[MattP311]

UCUM Application NSWHP.xlsx

New South Wales Health Pathology is in the process of configuring a new state-wide laboratory information system. As an integral part of this process we are reviewing all required units of measure for pathology testing and ensuring that they comply with both UCUM and RCPA requirements. We would like to apply for a range of new units to be included for use in pathology testing. Please see the attached document.

Thank you for your review
Matthew Powell

[SRKid]

Here is ChatGPT's analysis of this request:

Subject: Review of UCUM Application NSWHP.xlsx – Proposed Units for Pathology and Cellular Therapy

1. OverviewNew South Wales Health Pathology (NSWHP) has proposed several unit expressions for inclusion in UCUM, primarily for use in cellular therapy and advanced pathology reporting. The requested units are: 104/kg, 105/mL, 108/kg, 109/kg, and 10*11.
   Each expression is intended to denote count-based magnitudes (e.g., viable cell concentrations or doses) used in cell and gene therapy dose formulations, such as “1 × 10⁶ CAR-T cells/kg.”

2. Technical UCUM AssessmentProposed UCUM Expression Syntax Valid Dimensionally Valid Equivalent Canonical Form UCUM Change Required
   104/kg Yes Yes 1E4 · kg⁻¹ No
   105/mL Yes Yes 1E5 · mL⁻¹ No
   108/kg Yes Yes 1E8 · kg⁻¹ No
   109/kg Yes Yes 1E9 · kg⁻¹ No
   10*11 Yes Yes 1E11 No

All proposed expressions are fully UCUM-compliant and do not require addition of new atomic symbols. The numeric multiplier syntax (10X) is permitted per Section 38 of The Unified Code for Units of Measure (“Units with Numeric Multipliers”). These expressions are syntactically identical to existing UCUM representations such as 106/L and 10*3/uL widely used in hematology and microbiology.

3. Semantic and Clinical Context
   The submitted units align with conventions in cellular therapy, hematology, and immunology, where dose or concentration is expressed as a scaled count relative to patient mass or sample volume. Examples include:

• “2 × 10⁶ CAR-T cells/kg body weight”
• “3 × 10⁸ viable CD34⁺ cells/kg”
• “5 × 10⁹ platelets/kg”

These units express quantitative cell counts normalized to physiological parameters rather than new dimensional concepts. UCUM already supports such structure without schema modification.

4. Recommendations

5. Inclusion: No new base or derived unit definitions are necessary. These expressions may be optionally added to UCUM documentation as illustrative examples under 'COUNT-BASED UNITS IN CELLULAR THERAPY.'

6. Representation Best Practice: For data exchange (e.g., HL7 FHIR, LOINC, ISO 11240 contexts), values should preferably be transmitted as:
   • value = 2.3E9
   unit = {cells}/kg
   rather than embedding the scale factor in the UCUM unit. However, implementations using 10*9/kg are valid and parsable, ensuring backward compatibility.

7. RCPA Alignment: The proposals are consistent with the Royal College of Pathologists of Australasia (RCPA) reporting conventions for stem-cell and CAR-T dosing.

8. Suggested Annotation (Optional):
   •

9. Conclusion
   The NSWHP submission represents an appropriate and standards-compliant application of UCUM numeric multiplier notation.

• Conforms to UCUM syntax and dimensionality
• Reflects current scientific usage in cellular therapy
• Does not require new UCUM term additions

Recommended disposition: Accept for use under current UCUM specification; document as a valid example in pathology/cell-therapy guidance.

References

• UCUM Specification, §38 “Units with Numeric Multipliers”
• ISO 80000-1:2022, Quantities and units – Part 1: General
• NEJM 2023; 389:1331-1345 (CAR-T therapy dosing examples)
• PMC7315024 (Cellular therapy manufacturing metrics)