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Samples : Policy for Rejection
| Samples will be rejected for analysis if: |
| 1. The sample has been collected inappropriately. |
| 2. The sample is grossly haemolysed. |
| 3. The sample is grossly lipaemic. |
| 4. The sample has leaked from the container and, therefore, does not conform with Health & Safety Regulations. |
| 5. The sample is unlabelled or incorrectly labeled. |
| Our policy is to advise the requester either by telephone, or by letter as soon as possible, and to follow this up with written confirmation. The Laboratory will do everything it can for the test to be satisfactorily completed. |
Also refer to the Pathology sample and request form rejection policy  |
Sample Requirements : Adults
- 4.5 ml Vacutainer tubes are available for Biochemical tests. A list of analytes is shown below.
|
- One SST (orange cap) tube is sufficient for Profile, LFT and Cardiac enzymes.
|
- An extra tube is required for additional tests.
|
- Red cap tubes should be used for non-routine Biochemistry tests and Therapeutic drugs.
|
Adults Plain Tubes (SST Gel) 
| Alkaline Phosphatase |
LH |
| Alanine Transaminase (ALT) |
Lithium (pre dose) |
| Amylase |
Magnesium |
| Bilirubin |
Oestradiol |
| Bile Acids |
Osmolality |
| Ca-125 |
Paracetamol |
| Calcium |
Phosphate |
| CEA |
Potassium |
| Chloride |
Prolactin |
| Cholesterol |
PSA |
| Cholinesterase |
Salicylate |
| Cortisol |
Sodium |
| Creatinine |
Testosterone |
| CRP |
free T3 |
| Creatine Kinase |
free T4 |
| Protein Electrophoresis |
TFT |
| FSH |
Triglyceride |
| Gamma Glutamyl Transferase (GGT) |
Troponin T |
| HDL - Cholesterol |
TSH |
| Immunoglobulins: IgG, IgA, IgM |
Urea |
| LDH |
Uric Acid |
| LFT |
|
Adults
Plain Tubes (No Gel) 
| Alpha1 Acid Glycoprotein (A1AG) |
Haptoglobin |
| Alpha1 Antitrypsin (AAT) |
IgE |
| Beta2 Microglobulin |
Iron |
| B12 * This tube preferred, but will accept in yellow tube (no gel) |
Phenytoin * |
| Caeruloplasmin |
Phenobarbitone * |
| Carbamazepine * |
Progesterone |
| Copper |
RAST |
| Digoxin * (At least 6 hrs post dose) |
Theophyline * |
| Ferritin |
Zinc |
| 17-OHP |
Androstenedione |
| SHBG |
DHAS |
| Growth hormone |
IGF-I |
| PTH (EDTA sample preferred) |
Thyroglobulin |
| Folate * |
TTG (Tissue Transglutamase) |
|
| * B12 and Folate samples can be left overnight in a fridge but must reach the Laboratory the next day for reliable results. |
| * For therapeutic drug monitoring, we generally recommend that the sample is taken pre-dose, so that the analytical result reflects a 'trough' level except for Digoxin when the sample should be taken 6 hours post dose. |
Adult Anticoagulated tube (Fluoride oxalate)  |
| Alcohol* |
Glucose |
HbA1c (Glycated Haemoglobin) |
| *must have two grey top samples for Blood Alcohol analysis |
Adult Anticoagulated tube (Lithium heparin)  |
| Aluminium |
Plastic tube only |
| Carboxyhaemoglobin |
|
| Insulin/C-Peptide |
Only analysed if glucose <2.5 mmol/L.
Specimen must arrive in Lab. immediately |
Adult Anticoagulated tube (EDTA)  |
| Lead |
Blood Porphyrins (protect from light) |
| Red Cell Folate |
PTH* |
| *a gel or plain tube will also be required for calcium analysis, whenever PTH is requested. |
Sample Requirements : Paediatrics
| Small volume sample tubes are available for Paediatric samples (neonates and infants). |
|
| Baby samples MUST NOT BE labelled with Maternal PID. This is an unnecessary and dangerous practice. |
|
| The following is a list of minimum paediatric sample volumes: |
| NB: Please use 4.5 ml tubes for older children where possible. |
| Paediatric Paediatric Orange Cap (Lithium Heparin) |
| Suitable for routine biochemistry :-
e.g. U&E, Profile, LFT, Ca/Alb, Lipids : One tube filled completely |
| Additional requests :-
e.g. TFTs, Fractionated Bilirubin : Require 1 additional tube |
| Paediatric Paediatric Yellow Cap (Fluoride oxalate) |
| Blood Sugars : 1 tube completely filled
HbA1c : 1 tube completely filled |
| Paediatric Paediatric White Cap (No anticoagulant) |
| B12, Folate, Ferritin : 1 tube completely filled
Immunoglobulins/electrophoresis : 1 tube completely filled
TTG : 1 tube completely filled
Drugs :- Theophyline, Paracetamol, Salicylate : 1 tube completely filled |
Faecal Tests
| Random Sample Blue Cap |
| Fat Globules |
| Occult blood (FOB) |
| Porphyrins : Protect from light |
| Reducing substances : Fresh sample to Lab within 4 hr |
| Elastase |
Urine Tests : Adults & Paediatrics
| Random Sample White Cap (No preservative) |
| Amino Acids |
| Bence Jones Protein |
| Bile Pigments : Protect from light |
| Drugs of Abuse Screen |
| Metabolic Screen |
| Methylmalonic acid |
| Microalbumin |
| Mucopolysaccharides |
| Organic Acids |
| Osmolality |
| Reducing substances : fresh sample to Lab within 4 hour |
| Urine Porphyrins : Protect from light |
| Urobilinogen |
Urine Tests : Adults & Paediatrics - Timed Collections
|
24 hr Urine Collection - No Preservative |
| Calcium |
Sodium |
Phosphate |
Creatinine Clearance |
| Steroid Profile |
Urinary free cortisol |
Oxalate |
Urea |
| Potassium |
Uric Acid |
|
|
|
24 hr Urine Collection - Acid Preservative |
| Catecholamines (incl. Adrenaline, Noradrenaline, Dopamine) |
| 5-Hydroxyindole acetic acid (5HIAA) |
Reference Ranges
| See Table in "Reference Values" link at the top of this page. This table is only an approximate guide, as the majority of reference ranges are age related, and quoted on the report form. Therefore, it is important that a patient's date of birth is recorded clearly on the request form. Contact Duty Biochemist for any queries. |
Key Factors affecting Results
| 1.Common causes of spurious results due to incorrect collection or storage |
| Problem |
Cause(s) |
Affects |
| Delay in processing |
- Overnight storage
- Delay in transit
|
Increases potassium, & phosphate |
| Incorrect storage |
Storage of samples overnight in fridge |
Increases potassium & decreases bicarbonate |
| Haemolysis |
- Forcing blood through needle into tube
- Difficult to bleed patients (e.g. paeds)
- Storage frozen
- Very delayed samples
|
Increases potassium, phosphate, bilirubin. Also increases AST, LDH, CK and decreases Troponin T & glucose |
| Incorrect sample site |
Sample taken from drip arm |
Increased drip analytes e.g. glucose, potassium etc. Dilutional effect lowers other analyte concentrations |
| Incorrect sample tube |
Contamination of red/ yellow top tubes with blood containing EDTA (from purple top tube) |
Increased potassium & Decreased calcium, alkaline phosphatase, iron, magnesium |
| Lipaemia (fatty sample) |
Sample taken shortly after fatty meal |
Decreases sodium. Affects other analytes if severe |
| 2. Analytes requiring special conditions |
| Analyte |
Sample Tube |
Special Conditions |
| ACTH |
Adult Purple Top Tube (EDTA) |
Send to lab ASAP (within 15 mins). Transport on ice if possible. |
| Ammonia |
Adult Purple Top Tube (EDTA) or Red Top Pediatric sample (Paeds) |
Send to lab ASAP (within 15 mins). Notify lab before taking. Avoid haemolysis. |
| Calcitonin |
Adult Red or Yellow Top Tube |
Send to lab ASAP (within 15 mins). Transport on ice if possible. |
| Glucose |
Adult Grey Top Tube (Fluoride oxalate) or Yellow Top Pediatric sample (Paeds) |
Yellow/red top tubes are acceptable from A&E as these samples are processed within 2 hours |
| Gut hormone profile |
Special green top tubes containing protein inhibitor |
Before taking contact Biochemistry who will provide tubes and ice |
| Homocystine |
Adult Red or Yellow Top Tube |
Send to lab ASAP (within 15 mins). Transport on ice if possible |
| Insulin/C-peptide |
Adult Grey Top Tube (Fluoride oxalate) or Yellow Top pediatric sample (Paeds) |
Send to lab ASAP (within 15 mins). Transport on ice if possible. Insulin is only sent for analysis if glucose < 2.5 mmol/L (unless specifically requested) |
| Lactate |
Adult Grey Top Tube (Fluoride oxalate) or Yellow Top pediatric sample (Paeds) |
Send to lab ASAP (within 15 mins). Notify lab before taking. Avoid haemolysis |
| PTH |
Purple Top Tube (EDTA) preferred but Red/Yellow Top Tubes acceptable |
Sample must be processed within 4 hours in Red/Yellow Top tubes but stable for 8 hours in EDTA |
| Renin |
Adult Purple Top Tube (EDTA) or Red Top pediartric sample (Paeds) |
Send to lab ASAP (within 15 mins). Do not use ice. Take sample after 15 mins recumbency |
| CSF Bilirubin (Xanthochromia) |
1 mL (last sample) required. Serum required for bilirubin and total protein. |
Send to lab ASAP (within 15 mins). Protect from light. Do not use air tube. |
| 3. Commonly Encountered Analytical Interferences (in Blue) or Biological Actions |
| Analyte |
Drug or Substance Interfering |
Effect |
| Alkaline Phosphatase |
Anticonvulsants, barbiturates, oral contraceptive |
Increase |
| EDTA contamination |
Decrease |
| Calcium |
Prolonged tourniquet use, Vit D, bendrofluazide |
Increase |
| EDTA or citrate contamination, citrated blood |
Decrease |
| Cholesterol |
Oestrogens |
Decrease |
| Creatinine |
High bilirubin (icterus) and lipid (lipaemia) |
Decrease |
| Gamma GT |
Anticonvulsants, barbiturates, alcohol |
Increase |
| Glucose |
Frusemide, thiaxides, corticosteroids, stress |
Increase |
| Potassium |
Insulin, corticosteroids, loop/thiazide diuretics |
Decrease |
| K+ sparing diuretics, ACE inhibitors |
Increase |
| Haemolysis, EDTA contamination, excess storage |
Increase |
| Prolactin |
Oestrogens, MAO inhibitors, cimetidine |
Increase |
| Sodium |
Lithium |
Increase |
| Diuretics, carbamazepine, fluoxetine, lipaemia |
Decrease |
| Thyroxine |
Amiodarone, pregnancy |
Increase or decrease |
| Oestrogens |
Increase |
| Phenytoin, corticosteroids, heterophilic antibodies |
Decrease |
| Note: Common analytical interferences are screened for and if detected no results will be reported for that analyte.
If an analyte is clinically very important e.g. creatinine in a liver patient suspected of hepatic-renal syndrome then contact the clinical team, who will advise on alternatives. |
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