Specimen Collection
No preservative or anticoagulants to be used, collect sample in a plain container. Ideally from both eyes and aspiration must be gentle to avoid contamination with retinal fragments.
Vitreous humour is viscous, hence requires pre-treatment. At LabPLUS, all vitreous humour samples are analysed following heat treatment (100
o
C for 5 minutes)(1). Heat treated samples are not suitable for enzyme and protein analysis.
2 mL Collect
Turnaround Time: Within 1 day
Assay Method
Roche Cobas
Diagnostic Use and Interpretation
|
Analyte
|
Clinical guidance ranges (2-5)
|
Interpretation of raised concentration (2-5)
|
|
Glucose
|
After death, vitreous humour glucose falls rapidly
|
Diabetes mellitus or diabetic ketoacidosis, stress response, cardiopulmonary resuscitation, shock, intracerebral haemorrhage, burns, electrocution
|
|
B-hydroxy-butyrate
|
0.1-1.0 mmol/L
|
Fasting, alcoholic ketoacidosis, diabetic ketoacidosis, stress response, hypothermia
|
|
Creatinine
|
<212 umol/L*
|
Poor renal function, large muscle mass, heat shock
|
|
Sodium
|
135-155 mmol/L*
|
Dehydration (interpret in conjunction with creatinine and urea), salt poisoning
|
|
Chloride
|
95-120 mmol/L*
|
Dehydration (interpret in conjunction with creatinine and urea), salt poisoning
|
|
Urea
|
<10 mmol/L
|
Poor renal function, upper GI haemorrhage
|
|
Lactate
|
|
If very high, may indicate lactic acidaemia (but may be formed perimortem)
|
|
Magnesium
|
<1.4 mmol/L*
|
Salt water immersion or drowning (interpret with sodium and chloride)
|
*Based on local data / opinion from local forensic pathologists.
Potassium: Potassium quickly leaks from the retina after death and hence vitreous potassium is not a reliable indicator of ante-mortem plasma potassium. Its reliability as a marker for post-mortem interval is also limited due to significant inter-individual variation.
Sodium and chloride: concentrations may fall after death, at rates of up to 1mmol/L per hour.
Urea and creatinine: relatively stable in post-mortem specimens.
-
McNeil AR, Gardner A, Stables S. Simple method for improving the precision of electrolyte measurements in vitreous humor. Clin Chem. 1999;45(1):135-6.
-
Marshall WJ, Lapsley M, Day AP, Ayling RM. Clinical biochemistry : metabolic and clinical aspects. Third edition.. ed: Edinburgh : Churchill Livingstone Elsevier. 2014.; 2014.
-
Saukko P, Knight B. Ch 2 The Pathophysiology of Death. In: Knight's Forensic Pathology 3
rd
Ed. Edward Arnold Publishers 2004.
-
Coe JI. Postmortem chemistry update. Emphasis on forensic application. American Journal of Forensic Medicine and Pathology 1993;14(2):91-117.
-
Clinical guidance ranges were derived from local data, literature review and in discussion with local forensic pathologists.
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