Osmolality (Blood)

Testing Laboratory

Northland Te Tai Tokerau | Whangarei Base Hospital

Department

Chemical Pathology

Delphic Registration Code (Alpha Code)

SOS

Test Code (Numeric Code)

0122

Laboratory Handling

Sample Stability

4 days at 4°C

Associated Tests

• Osmolality (Urine)

Synonyms

Osmolality - calculated, Osmolality - serum, Fluid deprivation, Fuid deprivation test, Water deprivation test

Turnaround Time

8 hours

Specimen Type

• Plasma
• Serum

Specimen Requirements

Tube/Container Type:

Preferred

• Lithium Heparin PST- Gel (Light Green Cap)

Acceptable

• Lithium Heparin - Non-gel (Green Cap)
• Plain (Red Top)
• SST II (Gold Cap)

Preferred Sample Volume (ml)

4.5

Minimum Sample Volume (ml)

3.5

No of Samples Required

1

Paediatric Specimen Requirements

Tube/Container Type:

Preferred

• Lithium Heparin PST- Gel (Light Green Cap)

Acceptable

• Lithium Heparin - Non-gel (Green Cap)
• Plain (Red Top)

Preferred Sample Volume (ml)

0.5

Minimum Sample Volume (ml)

0.5

Pre-testing Requirements

Endocrinology Day Stay or within ADHB:
Please use dedicated "Fluid deprivation test" lab request form when sending samples for osmolality.
See link in 'Resources' under 'Additional Information' section to: CC6548 Laboratory Request Form: Endocrinology Day Stay Fluid Deprivation Test.

Additional Specimen Information

0.5 mL Paediatric Microtainer PST Blood (Preferred)
0.5 mL Paediatric Microtainer Heparin Blood
0.5 mL Paediatric Microtainer Plain Blood

Test Method

Performed in LabPlus Automation
Principle: Freezing Point Depression

Uncertainty of Measurement

4 mmol/Kg

[Note: This is an interim procedure for Specimen Services while GLCC has no osmometer available on site]

Greenlane staff:
1. Collect a matched blood and urine sample and record required information on dedicated request form.
2. Micro-sample collect or 5 mL blood. A minimum of 250ul serum or heparinised plasma is required and the blood should be collected with the minimum of stasis.
3. Send each set of specimens via taxi in an URGENT bag.
4. Phone Lablink (ext. 22000) to notify the chilly bin person that an URGENT fluid deprivation specimen is being sent.

Auckland (Specimen Services Staff at LabPLUS):
Once the specimens are received from Greenlane and time-stamped, Specimen Services staff is to:
1. Register tests as per the request form (refer to Internal request form examples, classification: LPALSREGIN024). [Note: Use the same request number for urine and plasma samples].
2. Check all details and registration requirements are correct.
3. Label specimens as per the Sample Numbering procedure (classification number: LPALSSPEPR057).
4. Give a copy of the request form and all specimens received to an Automation scientist to process URGENTLY.
5. If a sendaway test to Christchurch is requested, refer to the national sendaways instruction on Table 1, section 3.5 in the Sample Numbering procedure (classification number: LPALSSPEPR057).

Note: a dedicated EDTA tube is required for the sendaway antidiuretic hormone (ADHS) test to Christchurch.

Resources

• CC6548 Laboratory Request Form: Endocrinology Day Stay Fluid Deprivation Test

Contact Information