The list below includes Critical Callbacks and Courtesy Callbacks.

Critical results are defined as results that, if left untreated, could be life threatening or place the patient at serious risk. Critical results are those results from a clinical specimen that upon analysis are determined to be "critical" whether the specimen was submitted as a routine or stat specimen.

Critical test results will be communicated to the responsible licensed caregiver within 40 minutes from the time the result is available in the laboratory.

The 40 minute turnaround time is divided into:
- 30 minutes for the Laboratory turnaround time (time from when the test result is identified as critical to the time when the floor/practice receives the result).
- 10 minutes for the floor/practice turnaround time (time from when the floor/practice receives the result to the time when the result is communicated to the responsible licensed caregiver).

The laboratory in collaboration with the department or service involved in the monitor shall monitor the time between the identification of a critical value to the time it is reported to a licensed caregiver. Ongoing organizational efforts will target improvement in the timeliness of critical value reporting.

Courtesy callbacks are made in accordance with individual laboratory policy in an effort to improve clinical communication.

Approved by the MGH Medical Policy Committee (9/7/2005, 10/04/2006, 6/18/2008).

A related but distinct laboratory metric is Critical TESTS. Critical tests are defined as tests or procedures that must be conducted and reported quickly to determine the course of care. The MGH Pathology Critical TEST policy (in PDF format) can be found here.

Laboratory	Test	Value	Critical or Courtesy
Blood gas	All blood gas tests from a non-cardiac OR	All values	Courtesy
	Calcium, ionized	<0.8 or >1.54 mmol/L	Critical
	Hemoglobin	<6.5 g/dl	Critical
	PCO2 (arterial, venous, unknown)	<20 or >75 mmHg, first only (within past 24 hours)	Critical
	pH (arterial, venous, unknown)	<7.10 or >7.59 units, first only (within past 24 hours)	Critical
	PO2 (arterial, unknown)	<40 mmHg	Critical
Chemistry	Acetaminophen	>50 mg/L	Critical
	Bilirubin, total	>15 mg/dL (0-3 mo) >20 mg/dL (4-6 mo)	Critical
	Calcium	<6.5 or >14.0 mg/dl	Critical
	Carbamazepine	>20 mcg/ml	Critical
	Carbon dioxide (total)	<11 or >40 mmol/L	Critical
	Digoxin	>2.5 ng/ml	Critical
	Glucose, CSF	<40 mg/dl	Critical
	Glucose, plasma	<40 or >500 mg/dl	Critical
	Glucose, plasma	All results from Blake 13	Courtesy
	Isopropanol	>100 mg/L	Critical
	Lithium	>2.0 mmol/L	Critical
	Magnesium	<1.0 or >4.9 mEq/L	Critical
	Methanol	>100 mg/L	Critical
	Osmolality, plasma or serum	<250 or >335 mOsm/kg water	Critical
	Phenobarbital	>70 mcg/ml	Critical
	Phenytoin	>30 mcg/ml	Critical
	Phosphorus	<1.1 mg/dl	Critical
	Potassium	<2.8 or >6.0 mmol/L	Critical
	Sodium	<120 or >160 mmol/L	Critical
	Toxicology (serum)	Various toxic drug levels	Courtesy
Hematology	All hematocrits	>56%	Critical
	Delta values	WITHIN THE LAST 30 DAYS: Hematocrit >25% and decrease of ≥8% Hematocrit >20 and ≤25% and decrease of ≥4% Platelets <50 and decrease is equal to or >50%	Courtesy
	Differential	Presence of blasts on initial smear within 30 days	Critical
	Initial hematocrit	< or = to 20% within 30 days	Critical
	Initial platelet count	<40,000 or >999,000 within 30 days	Critical
	Initial WBC	<1,500 or >50,000 within 30 days	Critical
	INR	INR > or = to 5.0	Critical
	Partial thromboplastin time	>100 seconds	Critical
	Platelets	All pediatric patients <20 years old with a platelet count of <20,000	Critical
	Differential	All pediatric patients <20 years old with the presence of blasts on peripheral blood smear	Critical
Immunology	Cryocrit	5% or higher	Courtesy
	IgA	<7 mg/dL	Courtesy
	IgG	<200 mg/dL	Courtesy
	Viscosity	>3 relative viscosity units	Critical
Microbiology	Acid-fast smears	All positives	Courtesy
	Blood and CSF cultures	Cultures positive for bacteria, fungi, yeast or acid-fast organisms	Critical
	Cryptococcal and bacterial antigen tests	Positive	Courtesy
	Cultures	Positive for mycobacteria	Courtesy
	Cultures and direct FA	Positive for Legionella	Courtesy
	Fungal wet prep	Positive for mycelial elements	Courtesy
	Gram Stains	All stat requests	Critical
	Heterophile (inpatients only)	Positive	Courtesy
	Parasitology exams	All pathogenic positives	Courtesy
	Stool cultures	Cultures positive for enteric pathogens	Courtesy
	Syphilis serology (Inpatients only)	High titer positive	Courtesy
	Throat cultures	Cultures positive for group A beta strep	Courtesy
	VDRL on CSF	Positive	Courtesy
	Virology cultures, viral antigen tests, and viral PCR on CSF	All positives	Courtesy
Chelsea Health Center	Bilirubin, total	>15 mg/dL (0-3 mo) >20 mg/dL (4-6 mo)	Critical
	Calcium	<6.5 or >14.0 mg/dl	Critical
	Carbon dioxide (total)	<11 mmol/L	Critical
	CBC	-Platelets <100,000/cmm (courtesy) -Platelets <20,000/cmm (critical) -Hematocrit <20% or >56% (critical) -WBC <2,000 or >50,000/cmm (critical)	Critical/Courtsey
	Differential	<20% polys and bands Presence of blasts	Critical
	Glucose	<40 or >500 mg/dl	Critical
	Magnesium	<1.0 or >4.9 mEq/L	Critical
	Phosphorus	<1.1 mg/dL	Critical
	Potassium	<2.8 or >6.0 mmol/L	Critical
	RPR	Reactive	Courtesy
	Sodium	<120 or >160 mmol/L	Critical
Revere Health Center	CBC	-Platelets <100,000/cmm (courtesy) -Platelets <20,000/cmm (critical) -Hematocrit <20% or >56% (critical) -WBC <2,000 or >50,000/cmm (critical)	Critical/Courtesy
	Differential	<20% polys and bands Presence of blasts	Critical
	Stool guaiac	Positive	Courtesy
	Whole blood glucose	<40 or >500 mg/dl	Critical