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Chemical Pathology Service

Chemical Pathology can carry out routine and out-of-hours requests.

Routine requests

Samples for analysis should arrive in the laboratory as early as possible each morning. The laboratory will endeavour to provide results the same day on all specimens received before 8.00pm which are performed ‘in house’. Please see test repertoire.

Out-of-hours requests

The following investigations are available out-of-hours.

Tests that can be performed out-of-hours

Serum

  • Alcohol*
  • Ammonia (hand deliver)
  • Amylase
  • b-HCG
  • Bilirubin
  • Calcium Profile
  • CRP (C-Reactive Protein)
  • Creatine kinase
  • Digoxin
  • Glucose
  • Gentamicin
  • Iron
  • Lipid Profile
  • Lithium
  • Liver Profile
  • Magnesium
  • Osmolality
  • Paracetamol (take sample at least 4 hours post-ingestion)
  • Phenytoin
  • Random Cholesterol
  • Salicylate (only if clinically indicated; not as routine OD screen)
  • Theophylline
  • Troponin I
  • Urea and Electrolytes
  • Uric acid
  • TSH**
  • FT4**
  • FT3**
  • Folate**
  • Ferritin**
  • B12**
  • Cortisol**
  • Vitamin D**

*Alcohol is not to be requested routinely, on A&E patients smelling of alcohol.

**Available 9.00am to 8.00pm during weekends and Bank Holidays.

Whole blood

  • Blood gases
  • Carboxyhaemoglobin 

Urine

  • Electrolytes
  • Osmolality
  • Protein

Cerebrospinal fluid

  • Glucose (should be accompanied by a serum glucose)
  • Protein

Guidance for out-of-hours requesting

The following table provides guidance in the use of the available out-of-hours investigations by detailing clinical conditions in which they may be of value. Inclusion of a clinical condition or situation in this list does not imply that the investigation must always be done. The requesting clinician must exercise his/her clinical judgement and only request those tests that will influence the immediate management of the patient.

Indiscriminate use of the emergency service will be investigated by the Chemical Pathologist.

Biomedical investigations and clinical conditions/situations

Amylase

Abdominal pain with a high index of suspicion of pancreatitis.

β-HCG

Ectopic pregnancy – only if the result will influence the immediate management of the patient, otherwise take the sample and send to the laboratory for later analysis.

Calcium

Acute pancreatitis.

Clinical signs or symptoms suggestive of hypo/hypercalcaemia.

Massive transfusion.

Post-thyroidectomy or parathyroidectomy.

Digoxin

Compliance/toxicity.

Prior to further therapy if already on treatment.

Glucose

Confusion, stupor or coma.

Diabetes.

Poisonings – especially paracetamol and salicylate.

Iron

Definite or suspected overdose.

Lithium

Toxicity.

Definite or suspected overdose.

Magnesium

Resistant hypocalcemia.

Unexplained fits (Serum calcium = first line).

Osmolality

Hyponatraemia.

Poisonings.

Paracetamol

Definite or suspected overdose.

Note: take sample at least 4 hours post ingestion.

Phenytoin

Compliance/toxicity.

Prior to further therapy if already on treatment.

Salicylate

Definite or suspected overdose – but only if suspected clinically (not as a routine screening test).

Theophylline

Compliance/toxicity.

Prior to further therapy if already on treatment.

Urea and electrolytes

Cardiac arrhythmias.
Dehydration.
Diabetes mellitus.
Intensive IV therapy.
Metabolic confusion, stupor or coma.
Myocardial infarction.
Patients on drugs which affect electrolyte balance or are affected by electrolyte imbalance.
Renal impairment.
Shock.

Blood Gases

Cardiac/respiratory arrest.

Diabetes mellitus.

Metabolic confusion, stupor or coma.

Poisonings.

Respiratory problems.

Shock.

Carboxyhaemoglobin

Definite or suspected exposure to carbon monoxide.

Urine osmolality and/or electrolytes

Hyponatraemia.

Renal failure.

Cerebrospinal fluid (CSF)

Bacteriological investigation is of prime importance and preferred to biochemistry but protein and glucose may be of assistance - if the bacteriology is equivocal, or there has been partial antibiotic treatment.

Requests for ‘xanthochromia screening’ should be limited to those cases in which there is:

  • genuine clinical suspicion of subarachnoid haemorrhage
  • the presenting headache was at least 12 hours ago
  • and the scan is negative

The sample should be:

  • the last CSF sample obtained
  • collected into a plain tube
  • at least 0.5 mL volume
  • and protected from light - sent to the laboratory in a brown paper envelope along with a completed request form

Xanthochromia requests are analysed at Rotherham Hospital.

Requests for CSF oligoclonal bands must be accompanied by a serum sample. Do not use the vacuum delivery system for the transport of CSF samples (or any other ‘precious’ specimens).

All other tests out-of-hours

It may be possible to provide analyses not listed above out-of-hours, if they are essential for immediate patient management but all such requests must be discussed with the Duty Biochemist.

A medically qualified Consultant Biochemist or Chemical Pathologist is always available to discuss individual cases.

The laboratory will advise how to contact the duty clinician.