TABLE OF CRITICAL LIMITS


TABLE OF CRITICAL LIMITS CLINICAL CHEMISTRY Test Glucose Potassium Calcium Sodium


CO2 content Magnesium


Phosphorus Bilirubin Chloride Osmolality Urea nitrogen Uric acid CSF glucose Creatinine Ionized calcium4 Lactate


Hematocrit Hemoglobin Platelets


WBC count PT


PTT Fibrinogen


pCO2 pH


pO2


mmol/L mg/dL


mmol/L


mmol/L mg/dL


mmol/L mmol/L


mmol/L mg/dL


mmol/L mg/dL


µmol/L mg/dL


mmol/L mmol/kg


mmol/L mg/dL


µmol/L mg/dL


mmol/L mg/dL


µmol/L mg/dL


mmol/L mg/dL


mmol/L mg/dL


L/L g/L


×109 ×109 s s


/L /L


Adult LOW LIMIT


Units Mean (SD)


2.6 (0.4) 46 (7)


2.8 (0.3)


1.65 (0.17) 6.6 (0.7)


120 (5) 11 (2)


0.41 (0.16) 1.0 (0.4)


0.39 (0.10) 1.2 (0.3)


— —


75 (8) 250 (13)


— —


— —


2.1 (0.6) 37 (10)


— —


0.82 (0.14) 3.29 (0.56)


— —


Range


1.7-3.9 30-70


2.5-3.6


1.25-2.15 5.0-8.6


110-137 5-20


0.21-0.74 0.5-1.8


0.26-0.65 0.8-2.0


— —


60-90 230-280


— —


— —


1.1-2.8 20-50


— —


0.50-1.07 2.00-4.29


— —


HEMATOLOGY 0.18 (0.05) 66 (17) 37 (18)


2.0 (0.7) — —


g/L mm Hg


mm Hg kPa


0.88 (0.17)


0.12-0.30 40-120 10-100 1.0-4.0 — —


0.50-1.00


BLOOD GASES AND PH 19 (3)


9-25


7.21 (0.06) 43 (6)


5.7 (0.8) 7.00-7.35


30-55 4.0-7.3


C HIGH LIMIT Mean (SD)


26.9 (8.0) 484 (144)


6.2 (0.4) 8.0 (hemolyzed)


3.22 (0.22) 12.9 (0.9)


158 (6) 40 (3)


2.02 (0.82) 4.9 (2.0)


2.87 (0.48) 8.9 (1.5)


257 (86) 15 (5)


126 (12) 326 (18)


37.1 (21.1) 104 (59)


773 (119) 13 (2)


24.3 (11.4) 438 (206)


654 (380) 7.4 (4.3)


1.55 (0.19) 6.21 (0.76)


3.4 (1.3) 30.6 (11.7)


0.61 (0.06) 199 (27) 910 (147) 37.0 (20.7) 27 (9)


68 (33) 7.75 (2.63) 67 (6) 7.59 (0.03)


— —


Range


6.1-55.5 110-1000


5.0-8.0


2.62-3.49 10.5-14.0


145-170 35-50


1.03-5.02 2.5-12.2


2.26-3.23 7.0-10.0


86-513 5-30


115-156 295-375


14.3-107.1 40-300


595-892 10-15


13.9-38.9 250-700


177-1326 2.0-15.0


1.30-2.00 5.21-8.02


2.3-5.0 20.7-45.0


0.54-0.80 170-300 555-1000 10.0-100.0 14-40 32-150


5.00-10.00 50-80 7.50-7.65


— —


crossmatch, tests positive for syphilis (RPR or VDRL). For microbiology and parasitology—positive results from Gram stain or in culture from blood, cerebrospinal fluid, or body cavity fluid; positive India ink preparation; positive rapid antigen detection by agglutination tests for Cryptococcus, group B streptococci, Haemophilius influenzae b, or Neisseria meningitidis, positive results from acid-fast bacillus stain or culture; Salmonella, Shigella, or Campy- lobacter on stool culture; presence of malarial parasites. For clinical microscopy and urinalysis—elevated white blood cell count in CSF; presence of malignant cells, blasts, or microorganisms in CSF or body fluids; combination of strongly positive test results for glucose and for ketones in urine; presence of pathologic crystals (urate, cysteine, leucine, or tyrosine) on urinalysis. For hematology—listed frequently are the presence of blasts on blood smear; new diagnosis or findings of leukemia; presence of sickle cells (or aplastic crisis). Listed occasionally are plasma cells, band cells, atypical lymphocytes, and abnormal reticulocyte count.


include the following: For blood bank and immunology—incompatible 6 CLR 2023-2024 • MLO • www.clr-online.com


Adult table modified with permission by JAMA, Vol. 263, pp. 704-707, 1990. This table was updated by Dr. Gerald Kost in 2023. CSF, cerebrospinal fluid; WBC, white blood cell; PT, prothrombin time; PTT, partial thromboplastin time. Qualitative critical results for adults1


ritical limits define the boundaries of life- threatening diagnostic test results. Critical


results falling outside high and low critical limits must be reported to clinicians without delay, so the patient can be treated promptly if necessary. Critical value reporting was first implemented by George Lundberg, MD, and published in MLO in 1972. These tables are based on three national surveys by Gerald Kost, MD, PhD, MS, of UC Davis Health. Adapted with permission from his articles,1-3


they summarize critical limits used by 92 responding U.S. medical centers, including 20


trauma centers, and by 39 children’s hospitals. Mean low and mean high figures may be consid-


ered critical limits for each test listed. The frequency with which critical limits were listed can be found in the original articles. Dr. Kost conducted an indepen- dent national survey to determine ionized calcium critical limits.3


patient outcomes appeared in MLO4


His overview of critical limits and followed by


calls for national harmonization and standards of care for critical value practices.5,6 The Joint Commission identifies critical values and the need to report critical results timely in National Patient Safety Goals.7


Elements of per-


formance comprise: (a) define critical values and develop written procedures for managing critical results, by whom and to whom they are reported, and acceptable lengths of time between resulting and reporting; (b) implement procedures for man- aging critical results; and (3) evaluate the timeliness of reporting. Laboratories should carefully monitor failed clinician notifications and strive for none. Surveys and practice reviews are advancing harmonization8


practices in Australia,9 tia,17


Iran,18-20 Italy,21,22 South Africa,26


of critical values and notification Canada,10 Kuwait,23


China,11-16 Turkey,24


and the U.S.27-28 Croa- Spain,25 Understanding


), and national norms will be necessary to enable a global standard. Special considerations for newborn and pediatric critical values are neces- sary because of rapid adaption to the extrauterine demands for physiological changes. Studies address critical values for cytology,29,30 cytogenetics and molecular genetics,31 glucose,32 thology.34


quantitative critical limits, qualitative critical values, alternate nomenclature (e.g., “critical-risk results, significant-risk results, and alert thresh- olds”27


point-of-care virology,33 cal value results.35 and anatomic and surgical pa-


One US study addressed false positive criti- If institutions list COVID-19 tests,


then both false positive and false negatives should be of concern, the former for triggering unneces- sary isolation and the latter, for spreading disease by those unaware of infection.36


improve the performance of COVID-19 testing37


Repeat testing will but


may not be indicated for other critical results.19,24,38,39 Lifesaving diagnostic speed and accurately in- formed decision-making lead to appropriate therapy in times of human crises.40


Clinical laboratories and


point-of-care specialists can assign critical values and develop notification practices collaboratively with emergency physicians, hospitalists, and other clinical colleagues to achieve optimal outcomes for patients.


REFERENCES


1. Kost GJ. Critical limits for urgent clinician notification at U.S. medical centers. JAMA. 1990;263:704-707.


2. Kost GJ. Critical limits for emergency clinician notification at U.S. children’s hospitals. Pediatrics. 1991;88:597-603.


3. Kost GJ. The significance of ionized calcium in cardiac and critical care. Availability and critical limits at U.S. medical centers and children’s hospitals. Arch Pathol Lab Med. 1993;117:890-896.


4. Kost GJ. Using critical limits to improve patient outcomes. MLO. 1993;25(3):22-27.


5. Kost GJ. Co-creating critical limits for enhanced acute care: proven need and web knowledge base. Part 1: A call to action! MLO. 2015;47(12):34, 36-37.


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