Critical Value Cut-Off Limits - Clinical Chemistry
Printer-friendly versionCritical value cut-off limits: updating limits in accordance to guidance published by the Royal College of Pathologists.
Where applicable, the Clinical Biochemistry department has low and high cut-off values where in the event of results being out-with these limits, and being of new first-time occurrence, are telephoned to the requesting location.
The department has reviewed the existing critical cut-off values against that recommended by the Royal College of Pathologists’ publication, ‘The communication of critical and unexpected pathology results’ (October 2017), and have made the following changes to the cut-off values currently in place.
|
Test (units) |
Current PCH Cut-off Values |
RCPath 2017 Guidance |
2019 PCH Cut-off Values |
|||
|
Lower |
Upper |
Lower |
Upper |
Lower |
Upper |
|
|
Sodium (mmol/L) |
125
|
155 |
120 (>16yr) 130 (<16yr) |
160 |
120 (>16yr) 130 (<16yr) |
160 |
|
Potassium (mmol/L) |
2.5 |
6.5 |
2.5 |
6.5 |
2.5 |
6.5 |
|
Urea (mmol/L) |
|
30 |
|
30 (>16yr) ≥10 (<16yr) |
|
30 (>16yr) ≥10 (<16yr) |
|
Creatinine (umol/L) |
|
200 |
|
354 ≥200 (<16yr) |
|
200 |
|
AKI |
|
|
|
Stage 2/3 |
|
Stage 2/3 |
|
AKI/K+ |
|
|
|
Stage 1 with potassium >6.0mmol/L |
|
Stage 1 with potassium >6.0mmol/L |
|
Glucose (mmol/L) |
2.5
|
25 10 (pregnancy) |
2.5
|
25 (>16yr) ≥15 (<16yr)
|
2.5 |
25 (>16yr) ≥15 (<16yr)
|
|
CRP (mg/L) |
|
400 |
|
300 (GPs only) |
|
400 300 (GPs/OP) |
|
Adjusted Calcium (mmol/L) |
1.8 |
3.0 |
1.8 |
3.5 |
1.8 |
3.5 |
|
Magnesium (mmol/L) |
0.50 |
|
0.40 |
|
0.40 |
|
|
Inorganic Phosphate (mmol/L) |
0.4 |
3.5 |
0.3 |
|
0.3 |
|
|
ALT (U/L) |
|
900 (>16yr) |
|
15x ULN (900) |
|
900 |
|
CPK (U/L) |
|
5000 |
|
5000 |
|
5000 |
|
Troponin-T |
Not currently telephoned |
|
Local cut-off |
Not telephoned |
||
|
Amylase (U/L) |
|
500 |
|
5xULN (500) |
|
500 |
|
Lactate (mmol/L) |
|
5.5 |
No guidance |
|
5.5 |
|
|
Albumin (g/L) |
20 |
55 |
No guidance |
20 |
55 |
|
|
Total bilirubin (umol/L) |
|
270 |
No guidance |
|
270 |
|
|
Total Protein (g/L) |
25 |
90 |
No guidance |
25 |
90 |
|
|
Direct bilirubin (umol/L) |
Not currently telephoned |
|
25 |
|
25 |
|
|
AST (U/L) |
Not currently telephoned |
|
15xULN (525) |
|
525 |
|
|
GGT (U/L) |
|
2000 |
No guidance |
|
2000 |
|
|
Uric acid (umol/L) |
Not currently telephoned |
|
340 (antenatal) |
|
340 (maternity only) |
|
|
Bicarbonate (mmol/L) |
10 |
40 |
10 |
|
10 |
40 |
|
Bile Acid (umol/L) |
|
14 |
No guidance |
|
14 |
|
|
Salicylate (mg/L) |
|
400 |
|
300 |
|
300 |
|
Paracetamol (mg/L) |
|
200 |
|
Any detectable |
|
100 |
|
Carbamazepine (mg/L) |
|
25 |
No guidance |
|
25 |
|
|
Digoxin (ug/L) |
|
2.0 |
|
2.5 |
|
2.5 |
|
Theophylline (mg/L) |
|
25 |
|
25 |
|
25 |
|
Phenytoin (mg/L) |
|
25 |
|
25 |
|
25 |
|
Phenobarbitone (mg/L) |
|
70 |
No guidance |
|
70 |
|
|
Lithium (mmol/L) |
|
1.5 |
|
1.5 |
|
1.5 |
|
Iron (umol/L) |
|
34.5 |
No guidance |
|
34.5 |
|
|
Cortisol (nmol/L) |
Not currently telephoned |
50 |
|
50 |
|
|
|
(unless part of overnight dexamethasone suppression test) |
(unless part of overnight dexamethasone suppression test) |
|||||
|
Cortisol (SST 30min) (nmol/L) |
Not currently telephoned |
250 |
|
250 |
|
|
|
Ammonia (umol/L) |
|
50 |
|
100 |
|
100 |
|
Ethanol (mg/L) |
Not currently telephoned |
|
4000 |
Do not currently provide an urgent service |
||
Further communication will be issued in January prior to implementation. In the meantime, if you have any queries relating to this please contact the Biochemistry Department on 01733 678455 or email peh-tr.ChemImm@nhs.net
Kindest regards, Dr Mark Lum (Consultant Chemical Pathologist) and Jamie West (Biochemistry Manager).
