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Critical Values

Clinical Biochemistry: CLS and CRL



CLS and
Calgary Rural Labs (CRL)

Critical Values

To be called as soon as the result is available
24 hours per day.
All Patients,
Unless Otherwise Noted

Acetaminophen  Greater than 250 umol/L
Acetone  Greater than 6 mmol/L
Amikacin  Pre: greater than 10.0 mg/L
 Post: greater than 40.0 mg/L
 Random: greater than 40.0 mg/L
Amiodarone  Greater than 5.4 umol/L
Ammonia  Less than 17 years: greater than 110 umol/L
 17-150 years: greater than 200 umol/L
BHCG, Quantitative - Blood  Less than 16 years female: greater than 5 IU/L
BHCG, Qualitative - Urine  Less than 16 years female: positive
Bilirubin, Total

 Less than 31 days: greater than 300 umol/L
 Piccolo (for VHF testing) only - Less than 31 days: greater than 313 umol/L

 Blood Gases  CRL only: (EXCEPT Strathmore & Didsbury)
       pH: less than 7.30, greater than 7.51
       pCO2: less than 20 mm Hg, greater than 70 mm Hg 
       pO2: less than 60 mm Hg
       CO: greater than 9.9%
 Strathmore and Didsbury: no critical values apply
Calcium, Total  Less than 1.65 mmol/L
 Greater than 3.25 mmol/L
Calcium, Free or Ionized  Less than 0.85 mmol/L
 Greater than 1.50 mmol/L

 Greater than 65 umol/L

Carboxyhemoglobin  Greater than 7 years: greater than 9.9 %
Clozapine  Greater than 3500 nmol/L
Digoxin  Greater than 2.6 nmol/L
Ethanol  Greater than 65.0 mmol/L
 Not communicated to Emergency Departments at FMC, PLC, RGH and SHC.
Ethylene Glycol  Greater than 2 mmol/L
Gentamicin  Pre: greater than 1.9 mg/L
 Post: greater than 14.9 mg/L
 Random: greater than 14.9 mg/L
Glucose  Less than 30 days: 
        Less than 2.0 mmol/L
        Greater than 24.9 mmol/L
 30 days - 150 years:
        Less than 2.6 mmol/L
        Greater than 24.9 mmol/L 
Isopropanol  Greater than 8 mmol/L
Lactate  Greater than 4.0 mmol/L
Lithium  Greater than 2.00 mmol/L
Magnesium  Less than 0.40 mmol/L
 Greater than 1.90 mmol/L
Methanol  Greater than 2 mmol/L
Methemoglobin  Greater than 7 years: greater than 1.9 %
Oncology Cortisol  Oncology patients only: 
        Less than 50 nmol/L
Osmolality - Serum

 Acute care patients only:
        Less than 250 mmol/kg
        Greater than 320 mmol/kg
 Not communicated to Emergency Departments at FMC, PLC, RGH and SHC.

Overdose Iron  Less than 12 years: greater than 54 umol/L
Phenobarbital  Greater than 190 umol/L
Phenytoin (Dilantin)   Less than 4 months: greater than 80 umol/L
 4 months - 150 years: greater than 120 umol/L
Phenytoin, Free (Dilantin, Free)  Greater than 12.0 umol/L
Phosphate  Less than 0.40 mmol/L

 All: Less than 2.5 mmol/L
 Less than 4 months (venous): greater than 6.4 mmol/L
 Less than 4 months (capillary): greater than 7.3 mmol/L
 4 months - 150 years: greater than 6.0 mmol/L

Primidone (Mysoline)  Greater than 70.0 umol/L
Salicylate  Greater than 2.20 mmol/L
Sirolimus  Greater than 30 ug/L
Sodium  Less than 120 mmol/L
 Greater than 155 mmol/L
Spermatozoa - Urine  Less than 16 years female: Present
Tacrolimus  Greater than 30 ug/L
Theophylline  Greater than 110.0 umol/L
Tobramycin  Pre: greater than 1.9 mg/L
 Post: greater than 14.9 mg/L
 Random: greater than 14.9 mg/L
 ACH CF patients: greater than 25.0 mg/L
Troponin I Access 
 Greater than 0.50 ug/L
Troponin I Stratus 
 Greater than 0.50 ug/L
Troponin I Triage Meter
 VHF patients only: greater than 0.50 ug/L
Troponin I Vidas 
 Greater than 0.10 ug/L
Troponin T High Sensitivity

 Greater than 110 ng/L
 Emergency and inpatient critical TNT will not be communicated by telephone; only physicians of community patients with a critical value will be contacted.

Valproic Acid  Greater than 1150 umol/L
Vancomycin  Pre: greater than 25.0 mg/L
 Random: greater than 60.0 mg/L


Hematology: CLS and CRL


CLS and
Calgary Rural Labs (CRL)

Critical Values

To be called as soon as result is available 24 hours per day



Adults: equal to or less than 60 g/L
0-6 days: less than 100 g/L

Platelet Count

Less than 20 x 10E9/L

Absolute Neutrophil  Count

Less than 0.6 x 10E9/L

(* See note)

White Blood Cell Count (WBC) Less than 0.6 x 10E9/L
Greater than 99.9 x 10E9/L

Prothrombin Time (PT)

INR greater than 5.0

Activated Partial Thromboplastin Time (APTT)

Equal to or greater than 120 seconds



Less than or equal to 1.0 g/L

Heparin Induced Thrombocytopenia Antibody (HIT) Positive
*Note: All the differential results are phoned, not just the neutrophil count.


Appropriate medical staff will be notified by fax or phone of the following results:

1. Positive blood cultures

2. Positive central nervous system specimens (CSF, brain, etc.) cultures and gram stains

3. Positive tissue cultures (liver, bone biopsies, etc.)

4. Beta-hemolytic Streptococci, Group A from sterile sites

5. Neisseria gonorrhoeae from eyes

 6. Neisseria gonorrhea/Chlamydia - positive from female 0-15 years

7. Clostridium botulinum, Clostridium perfringens, Clostridium tetanus

8. Corynebacterium diptheriae

9. Legionella species
10. Listeria species
11. Positive Modified Acid Fast and Ziehl-Neelsen stains

12. Unusually resistant organisms including:

  • Vancomycin resistant Enterococci  (VRE)
  • Methicillin resistant Staphylococcus aureus (MRSA)
  • Multiply resistant gram negative or any other highly resistant organism with unusual suscetibility pattern. On Blood/Sterile fluids/Wound/AN02/Screening swabs, BAL, tracheal aspirates
  • Extended spectrum beta lactamases (ESBLs)
  • Glycopeptide intermediate Staphylococcus aureus (GISA), Borderline oxacillin resistant Staphylococcus aureus (BORSA)

13. All Notifiable Diseases isolates

14. Cryptococcus neoformans

15. Zygomycetes from sinus/eye specimens

16. Vitreous fluids from eyes (positive and negative reports from slide preparations)

17. Blastomyces dermatitidis, Histoplasma capsulatum, Coccidioides immitis, 
     Paracoccidioides brasiliensis, Sporothrix schenkii, Penicillium marneffi

18. Level III organisms: Bacillus anthracis, Brucella spp., Francisella spp., Yersinia

19. Stenotrophomonas maltophilia: non-sterile sites

20. Stool pathogens including Salmonella, Shigella, Yersinia, Campylobacter spp.,
     Clostridium difficile, E-coli 0157:H7, Vibrio spp.,

21. All positive and/or STAT Malaria tests

22. PCP - Pneumocystis jirovecii (carinii)

23. RSV, Influenzae A; all positive results

24. Varicella Zoster Virus: all positive results

25. Parasites:Cyclospora spp.,Giardia, Entamoeba histolytica, Cryptosporidium spp.,
     Acanthamoeba,  Parasitic ova, worm, proglottid, and larvae



  • Critical values are test results that are so abnormal that they generally indicate severe illness and require immediate medical intervention. For this reason, these values must be communicated to the attending physician immediately.
  • While critical values are generally indicative of acute disease requiring intervention, there are some patients with marked metabolic derangements that are physiologically fairly well compensated. For example, renal patients can have chronically elevated potassium levels that are surprisingly well tolerated. A general rule of thumb is that chronic changes in physiological status are much better tolerated than rapid alterations.
  • Some physicians or units may decline communication of critical values. In these cases, written documentation must be produced for the laboratory to comply with this request.

Some testing areas may wish to phone some abnormal results, and these discretionary decisions have not been built into the critical value list.