Pathology Phone Limits

Written by Aaron Doherty on 18 May 2026.

Pathology Phone Limits

By Department

Clinical Chemistry

Phoning and Critical Limits

Analyte	Phone results below or equal to:	Phone results above or equal to:	Units	Notes
Sodium	Adults: 120 Paediatrics: 130	160	mmol/L
Potassium	2.5	6.5	mmol/L
Urea	-	Adults: 30 Paediatrics: 10	mmol/L	Except those on renal wards or under renal consultants or from dialysis units
Creatinine	-	Adults: 354 Paediatrics: 200	umol/L	Except those on renal wards or under renal consultants or from dialysis units
eGFR	Adults: 15	-	ml/min
AKI	-	3		Do not phone on dialysis patients (often from dialysis units or renal wards – 3, 303, 305, HH5) Do not phone in CKD 4 or 5
Glucose	2.5	Adults: 25 Paediatrics: 15	mmol/L
Calcium adjusted	1.8	3.5	mmol/L
Magnesium	0.4	-	mmol/L
Phosphate	0.3	-	mmol/L
AST	-	600	U/L	Except those on liver wards or under liver consultants
ALT	-	600	U/L	Except those on liver wards or under liver consultants
Total CK	-	5000	U/L
Amylase	-	500	U/L
Digoxin	-	2.5	ng/mL
Theophylline	-	25	mg/L
Phenytoin	-	25	mg/L
Lithium	-	1.5	mmol/L
Troponin I	-	16 (female or unknown) 34 (male)	ng/L	GP only
Ammonia	-	100	umol/L	Paediatrics only
Ethanol	-	>10	mg/dL	Paediatrics only
Paracetamol	-	Paediatrics > 5 Adults > 50	mg/L
Salicylate	-	300	mg/L
Conj bilirubin (DBIL)	-	25	umol/L	Paediatrics only
Total bilirubin	-	225	umol/L	Paediatrics only
Carbamazepine	-	25	ug /mL
Iron	-	70	umol/L	ED only
Phenobarbitone	-	70	mg/L
CSF Glucose	3.3	-	mmol/L	Paediatrics only
CSF Protein	-	0.45	g/L	Paediatrics only
Lactate	-	2.3	mmol/L
CRP	-	300	mg/L	GP only
Total bile acids	-	20	umol/L	Obs/gynae only. Phoning protocol already agreed.
Urine protein:creatinine ratio		30	mg/mmol	Antenatal only, first raised result only
Methotrexate	Phone all		umol/L

Xanthochromia results phoned

Oxyhaemoglobin is present in sufficient concentration to impair the ability to detect haemoglobin. SAH not excluded.
Increased CSF bilirubin. Consistent with SAH (NB: this would be an unusual pattern within the first week after an event).
Increased CSF bilirubin. Consistent with SAH (NB: this would be an unusual pattern within the first week after an event).
Increased CSF bilirubin but probably totally accounted for by increase in serum bilirubin. Not supportive of SAH.
Bilirubin and oxyhaemoglobin increased. Consistent with SAH.
Increased CSF bilirubin. This finding may be consistent with: SAH; an increased bilirubin accompanying the increased CSF protein; or another source of CSF blood

Haematology

Haematology	Core hours**	Out of hours	All hours
Hb	<70g/L or >200g/L	<50g/L	Unexplained sudden drop in Hb >30g/L within 24hrs
MCV
Plt	New unexplained <50 x 10⁹/L or >1000 x 10⁹/L	Platelet count <20 x 10⁹/L
Wbc	New unexplained <2.0 x 10⁹/L or >50 x 10⁹/L
Neuts			New unexplained <0.5 x 10⁹/L
Other general rules	All newly presented Acute Leukaemia and CML
	Known Acute Leukaemia’s with blasts present
	Suspected relapse of Acute Leukaemia’s
	Blood film suggestive of Thrombotic microangiopathic anaemia (e.g. TTP, MAHA, HUS, DIC)
	Results that are not comparable to previous
	All hours
Infectious Mononucleosis	All Positives
Malaria	All Positives
Sickle Screen	All Positives (inpatient’s only)
FMH	All FMH Quantitation’s
G6PD	= or < 6.4 IU/gHb
Clotting Studies
INR	>5.0 (>6.0 Anticoagulant clinic)
APTT	APTT >4.0
Fibrinogen	Fibrinogen <1.0g/L
D-Dimer	> 250 ng/mL (GP/ Outpatients)
Special Coagulation (All results stipulated below will be telephoned to a Consultant Haematologist who will contact the requesting medical team)
ADAMTS13 Activity	< 10 IU/dL All new urgent or ? TTP
HIT screen	>1.0 IU/mL
First time Factor Assay	<10 u/dl
Positive Inhibitor	>0.6BU or any new patients
Urgent VWF	<15 IU/dL

All abnormal coagulation results must be telephoned regardless of previous results

Sickle screens should be phoned for all in-patients

Immunology

Autoimmunity
- New positive GBM antibodies
- New positive MPO antibodies*
- New positive PR3 antibodies*
*Low positive / equivocal anti-MPO / PR3 antibody results should be interpreted in the clinical context and decision to communicate is based on whether features of small vessel vasculitis are present or likely.
- New finding of positive LKM / SMA / SLA or LC-1 liver antibody in a child (<16 years) with very high ALT
Investigation of plasma cell dyscrasias (myeloma)
- Serum IgG paraprotein >15 g/L
- Serum IgA or IgM paraprotein >10 g/L
- IgD or IgE paraproteins regardless of concentration
- Light chain only kappa or lambda paraproteins with abnormal sFLCs ratio of >7 or <0.1 and involved light chain >100 mg/L.
- Any paraprotein / abnormal sFLCs ratio with significant symptoms indicating an urgent problem (e.g. spinal cord compression, acute kidney injury)
Suspected immunodeficiency
- Any result supporting a new finding of severe combined immunodeficiency (SCID) in a child should be communicated urgently to Paediatric Immunology.
- New severe T-cell lymphopenia
  - Adults: CD4+ T-cell count <200 cells/uL
  - Child ≥6 years: CD4+ T-cell count <200 cells/uL
  - Child aged 1 year to <6 years: CD4+ T-cell count <500 cells/uL
    - Child aged <1 year: CD4+ T-cell count <750 cells/uL
  - Marked hypogammaglobulinaemia

HPA Microbiology

Bacteriology

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

Virology

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

Created on 15 September 2010.
Last updated on 18 May 2026.