P23

Can Morning Serum Cortisol Ranges and Action Limits be Harmonised ?

Robert Wardrop1,*, Narelle Hadlow1

1Clinical Biochemistry, Pharmacolgy, Toxicology, PathWest Laboratory Medicine WA, Perth, Australia

Introduction: Harmonisation of reference intervals and common action limits1 aid in interpretation of important laboratory results. Morning cortisol is important for assessment of the HPA axis2,3   but has a significant time pattern and is affected by sunrise.4 Along with a lack of method alignment this potentially means any location in the world may need its own specific cortisol range.

Objectives: To extract cortisol data from four laboratories in Australia using identical methodology and compare potential diagnostic cut-offs in each population.

Methods: Serum sample data was extracted from four laboratories using the Siemens Advia Centaur Cortisol assay. Cortisols < 30 nmol/L and > 1000 nmol/L were excluded.  Samples taken between 07:00-11:00 with known sex and date of birth were analysed (N=88,480) and Multiple of Medians (MoM's) derived.

Results: Morning cortisol curves varied by location and were affected by sunrise and daylight saving times. Using raw cortisol cut offs of < 150 or 350 nmol/L resulted in high variation in the proportion of subjects falling below the cut off.  Use of a MoM Cortisol cut off of 0.30 and 0.90 MoM based on time of collection (MoM TOC) better aligned the proportion falling below these cut offs at all four cities. Adjusting for a cortisol median based on sunrise time (MoM SR) has some impact on the 0.30 MoM.

 

Brisbane

Melbourne

Perth

Sydney

Records

41,148

15,095

12,219

20,018

Collection Times

07:45

09:15

07:45

09:15

07:45

09:15

07:45

09:15

Mean     nmol/L

433

372

479

415

457

389

458

382

Median  nmol/L

417

344

470

398

449

370

450

364

% < 150  nmol/L

1.9%

4.1%

3.0%

5.3%

4.1%

3.9%

3.2%

4.6%

% < 350  nmol/L

30.2%

52.0%

22.0%

39.2%

20.1%

44.3%

24.4%

45.7%

MoM (TOC)

 

 

 

 

 

 

 

 

0.30 MoM

1.3%

1.7%

2.7%

4.5%

4.1%

2.2%

2.6%

2.5%

0.90 MoM

37.5%

40.7%

37.8%

40.7%

34.0%

39.4%

37.6%

39.7%

MoM (SR)

 

 

 

 

 

 

 

 

0.30 MoM

1.1%

1.8%

3.5%

4.5%

3.7%

2.1%

2.3%

2.6%

0.90 MoM

22.8%

45.7%

22.3%

40.9%

20.1%

42.0%

22.1%

42.4%


 

Conclusion: It is possible to harmonise cortisol ranges and action limits by using a MoM approach based on time of collection and it also allows for a broader collection time.

Keywords: Biochemistry, Blood, Other organ