Verification study on the NORIP LDH reference intervals with a proposed new upper reference limit.

Area of Science:

• Clinical Chemistry
• Laboratory Medicine
• Biochemistry

Background:

• The Nordic Reference Interval Project (NORIP) provides reference intervals (RI) for laboratory tests.
• Lactate dehydrogenase (LDH) is an enzyme found in many body tissues, and its levels can indicate cellular damage or disease.

Purpose of the Study:

• To verify the established serum lactate dehydrogenase (LDH) reference interval (RI) from the Nordic Reference Interval Project (NORIP).
• To assess the clinical applicability of the NORIP RI for LDH by comparing it with locally derived data.

Main Methods:

• Serum LDH concentrations were analyzed using the Dimension Vista 1500 system with an IFCC method.
• Retrospective data mining of clinical laboratory information systems was employed to calculate an indirect RI for LDH.
• Comparison of the calculated indirect RI with the existing NORIP RI for the adult age group (18 to <70 years).

Main Results:

• The study verified the transference of the NORIP RI for LDH, with minor bias observed against reference serums.
• An indirectly calculated RI for adults showed an upper limit of 240 U/L (90% CI: 234-243 U/L).
• A significant percentage (25.1%) of retrospective LDH test results exceeded the NORIP upper limit of 205 U/L, with variations based on the requesting clinical setting.

Conclusions:

• The current NORIP upper limit for serum LDH (205 U/L) may be too low, as evidenced by a high proportion of results exceeding this threshold.
• The findings suggest a need to re-evaluate and potentially adjust the NORIP upper RI for LDH to better reflect current clinical laboratory data.
• Further investigation into factors influencing LDH levels and reporting is warranted.