Clinical Decision Limits

Written by Craig Webster Created on Updated on .

Phoning limits for biochemistry tests are as follows:

Decision limits for phoning

  Below Above Units
Sodium 120 150 mmol/L
Potassium 3 6.5 mmol/L
Urea   30 mmol/L
Creatinine   500 umol/L
Glucose 2.5 20 mmol/L
Calcium adjusted 1.8 3.5 mmol/L
Magnesium 0.4   mmol/L
Phosphate 0.3   mmol/L
AST   700 U/L
ALT   400 U/L
Total CK   500 U/L
Amylase   600 U/L
TBA   20 umol/L
Iron   70 umol/L
Total bilirubin   225 umol/L
Carbamazepine   25 ug /mL
Digoxin   2.5 ng/mL
Theophylline   45 mg/L
Phenytoin   20 mg/L
Phenobarbitone   70 mg/L
Lithium  <0.2 >1.5 mmol/L
Valproate   100 mg/L
Cyclosporin A   200 ug/L


phoned with other abnormal results

Salicylate   20 mg/L
Paracetamol   10 mg/L
Ammonia All phoned    
Lactate All phoned    
beta-HCG All phoned    
progesterone All phoned    
CSF glucose All phoned    
CSF protein All phoned    
NNU results All phoned    


Immunology results to be telephoned:

  • CD4 count <200 cells/cumm or <10% on new patients (paediatric levels are different, but agreed with Paed consultants)
  • Lymphocyte subsets in infants <2yo: Any T cell subset below age-related normal range, any other abnormality suggesting SCID (e.g. MHC class II deficiency). (Note this is not exclusive: any abnormality may be discussed with requesting clinician)
  • New positive GBM antibodiest
  • New positive MPO antibodies
  • New positive PR3 antibodies
  • New paraprotein IgG , A or M  > 20g/L
    • IgD or IgE (any size)
    • serum monoclonal free light chains (any size, whether or not with intact paraprotein)

Abnormal Laboratory Test Results – Triggers for Telephoning Results Haematology

HaemoglobinWhite Blood Cell Count
<8.0 g/dl normochromic and normocytic Low result – neutropenia <0.5 x 10 9/L
<7.0 g/dl microcytic and hypochromic   High result – White cell count >40 x 10 9/L
<7.0 g/dl macrocytic  or Lymph count > 20 x 10 9/L
<5.0 g/dl renal patients Any presence of blast cells
PlateletsClotting Studies
Lower limit - <70 x 10 9/L   INR - >5.0
Upper limit - >1000 x 10 9/L   PTT - >180 seconds
  Fibrinogen < 1.0g/l
  • All Positive Malaria Screens
  • All Anti FXa results >1.20 iu/ml
  • If the patient is known to the department and has had a similar result within the previous 7 days then the urgent contact is not necessary.

HPA Microbiology – List of abnormal results telephoned to clinical staff


  • Gram stain results of positive blood culture on Day 1
  • Positive CSF results
  • Positive sterile site results
  • Significant in-patient results from enteric bench
  • Multi resistant gram negative and gram positive isolates including mupirocin resistant MRSA
  • Group B streptococcal isolates from neonates
  • Group A in patient isolates
  • Positive Legionella urinary antigen and Pneumococcal urine antigen results
  • Smear and culture positive Mycobacteria
  • Antibiotic assay results outside normal ranges
  • Any other significant results at the discretion of Medical Microbiologists


  • Serological evidence of acute infection with Hep A, Hep B and in pregnant patients CMV, Parvovirus and Rubella
  • New diagnoses of HIV
  • VZV IgG negative from exposed patients at risk of severe VZV infection
  • New diagnosis of Hep B, Hep C and HIV in haemodialysis patients
  • Evidence of Hep B/Hep C and HIV in needle stick injury source patients
  • Clinically important positive respiratory PCR results i.e.: influenza, RSV in immunocompromised patients
  • Positive PCR results in outbreaks
  • Positive blood PCR for CMV and Adenovirus
  • Negative blood results for CMV PCR
  • Significant blood PCR results for EBV and Polyomavirus
  • All positive PCR results on CSF specimens
  • All positive Chlamydia PCR results on eye swabs
  • All positive PCR results from neonatal unit