Plasma
CSF
Spot Fluid
Adult patient:
Fluoride tube
Minimum blood volume: 2 mL
Adult patient:
Fluoride tube
Minimum volume: 2 mL
Adult patient:
Fluoride tube
Minimum volume: 2 mL
Paediatric patient:
Paediatric fluoride tube
Number of vials: 1
Minimum blood volume: 1.3 mL
Paediatric patient:
Paediatric fluoride tube
Number of vials: 1
Minimum volume: 1.3 mL
Paediatric patient:
Paediatric fluoride tube
Number of vials: 1
Minimum volume: 1.3 mL
Authorisation code required
No
24 Hr available service
Yes
Yes
No
Method
Spectrophotometry
Reference interval
Plasma Glucose
Fasting plasma glucose:
| Non-diabetic: | < 5.6 |
| Impaired fasting glucose: | 5.6 - 6.9 |
| Diabetes mellitus: | > 7.0 |
DM diagnosis needs to be confirmed by repeat testing on a separate day or by OGTT.
(Source: modified from Diabetes Care 2010; 33 (Suppl): S62 - 9)
Oral glucose tolerance test:
| Normal | IFG | IGT | DM | |
| 0 min | < 5.6 | 5.6 - 6.9 | - | > 7.0 |
| 120 min | < 7.8 | - | 7.8 - 11.0 | > 11.1 |
(Source: Diabetes Care 2003; 26: 3160 - 67)
CSF Glucose
2.2 - 3.9 mmol/L
(Source: Roberts WL et al. Reference Information for the Clinical Laboratory. In Tietz Textbook of Clinical Chemistry and Molecular Diagnostics, 4th edn. Burtis CA, Ashwood ER and Bruns DE eds. Elsevier Saunders 2006; 2251 - 2318)
Clinical indication
Plasma:
Detection of hyperglycaemia and hypoglycaemia
Diagnosis and as a screening test for diabetes mellitus
Monitoring glycaemic control
CSF:
Aid in diagnosis of meningitis.
Result interpretation
Plasma:
In a patient with symptoms suggestive of diabetes mellitus, the finding of a fasting plasma glucose of
> 7.0 mmol/L on two occasions, or a plasma glucose of > 11.1 mmol/L at least two hours following a meal on two occasions, is diagnostic of diabetes mellitus.
In patients with fasting plasma glucose levels between 6.1 - 6.9 mmol/L or random plasma glucose levels between 7.8 - 11.0 mmol/L, an oral glucose tolerance test (OGTT) should be performed.
Fasting plasma glucose levels < 6.1 mmol/L and / or random levels < 7.8 mmol/L make diabetes mellitus unlikely, and OGTT is not indicated.
CSF:
CSF glucose must be interpreted with that of plasma glucose. In 70% bacterial meningitis cases, CSF / Plasma glucose ratio is < 0.31 while in 99% of cases, CSF glucose is < 1.9 mmol/L and CSF / Plasma glucose ratio is < 0.23 (vs viral meningitis).
(Source: Scheld WS. Bacterial meningitis, brain abscess and other suppurative intracranial infections. In Harrison's Principles of Internal medicine 14th edn. Fauci et al, eds. McGraw Hill Co. Inc. 1998; 2416 – 2434)
Measurement of uncertainty
Frequency of measurement
Daily