Specimen Collection

Sample stability:

• 4 hours at 20-25 ^o C
• 2 days at 2-8 ^o C
• 6 months at -20 ^o C

Freeze only once.

5 mL Adult PST Blood (Preferred)

0.5 mL Paediatric Micro-PST Blood (Preferred)

4 mL EDTA Blood

5 mL Heparin Blood

4 mL Plain Blood

3.5 mL SST Blood

0.5 mL Paediatric Microsample Blood

0.5 mL Paediatric Micro-heparin Blood
Reference Intervals

Units: mU/L

Reference interval: 2.6 - 24.9 (fasting)

Conversion factor: mU/L x 6.95 = pmol/L

Uncertainty of Measurement: 10%

Notes:

• Insulin antibodies may interfere with the measurement and interpretationof insulin levels in insulin treated diabetics.
• Haemolysis causes a false decrease in the insulin result.
  

Turnaround Time: Within 1 day
Assay Method

Principle : Sandwich type immunoassay with chemiluminescence detection

Assay : Roche Elecsys Insulin

Analyser : Cobas e801

Diagnostic Use and Interpretation

Investigation for insulinoma (or other causes of hypoglycemia)

It is essential to measure the insulin level at the time of documented hypoglycemia (blood glucose less than 2.5 mmol/L).

To achieve hypoglycemia it may be necessary to perform a prolonged fast under observation: see Fasting Hypoglycemia Test

In the presence of hypoglycemia, a plasma insulin less than 3 mU/L suggests a non-insulin mediated cause for the hypoglycemia. If greater than 3 mU/L it suggests insulinoma, nesdioblastosis, factitious insulin administration or sulphonylurea effect.

Sulphonylureas can be measured by HPLC by consultation with the Toxicology service via Lablink.

See: Sulphonylurea drug screen

See: Fasting Hypoglycemia Test

Assessment of insulin resistance

Serum insulin levels are poor measures of insulin resistance.

There is no clinical benefit in measuring insulin resistance for managing obesity, metabolic syndrome or PCOS in the general practice setting, and such requests will not be approved.

Calculation of the HOMA index of insulin resistance may be useful in assessing the probablity of NASH and the need for liver biopsy or bariatric surgery, and requests will be approved for these specific indications.

Testing for insulin analogs

There are no specific assays for insulin analogs. The insulin analogs Aspart, Lispro and Glargine show no detectable crossreactivity in the Labplus (Roche) assay. However, these analogues may be detected by Siemens Atellica assay used at North Shore Hospital. Testing by both assays can therefore be helpful in detecting the presence of these analogs.

References

1. Samaras, K., A. McElduff, et al. (2006). "Insulin levels in insulin resistance: phantom of the metabolic opera?" Med J Aust 185 (3): 159-61.

2. Stability of insulin in serum: Labplus in-house stability study (2009)

3. Owen, W. E. and W. L. Roberts (2004). "Cross-reactivity of three recombinant insulin analogs with five commercial insulin immunoassays." Clin Chem 50 (1): 257-259.

Contact Information

Emails to chemicalpathologist@adhb.govt.nz will receive priority attention from the on-call chemical pathologist.

If the query concerns a specific patient please include the NHI number in your email.

If email is not a suitable option, please contact the on-call chemical pathologist via Lablink (Auckland City Hospital ext. 22000 or 09-3078995).

Individual chemical pathologists may be contacted but will not be available at all times.

After-hours : contact Lablink (Auckland City Hospital ext. 22000 or 09-3078995) or hospital operator for on duty staff after hours.

Dr Samarina Musaad (Clinical Lead) : SamarinaM@adhb.govt.nz ext. 22402

Dr Cam Kyle: CampbellK@adhb.govt.nz ext 22052

Dr Weldon Chiu: WeldonC@adhb.govt.nz ext. 23427

Dr Campbell Heron: CHeron@adhb.govt.nz ext. 23427

Dr Sakunthala Jayasinghe: Sakunthala@adhb.govt.nz ext. 23427

Specimen Transport Instructions for Referring Laboratories

Outside laboratories: separate within 4 hours and send serum/plasma on ice or frozen to Labplus

Last updated at 15:26:00 06/01/2025