Medical Laboratory Observer’s annual reference guide, Clinical Laboratory Reference (CLR) is the industry’s only complete resource guide providing tables of critical values and high and low critical limits; cutoff concentrations for drug tests; critical limits for therapeutic drug levels; adult reference intervals; and pediatric reference intervals. CLR also provides an extensive, alphabetical  guide to tests, equipment, and services for the clinical lab market, along with company descriptions and contact information for ordering and pricing.

The tables of critical limits, critical values, and reference intervals help laboratorians interpret test results. Laboratory communication of abnormal test results is an essential aspect of patient care. Critical limits establish the upper and lower values that indicate when a patient’s medical condition may be precarious, requiring the immediate attention of the provider who ordered the test. A clinical laboratory critical value is a laboratory test result that falls significantly outside the normal reference interval and indicates a potentially life-threatening situation requiring immediate medical attention. Clinical laboratory reference intervals (also known as reference ranges) are the set of values used by healthcare providers to interpret laboratory test results. These intervals represent the expected range of values for a healthy population and help determine whether a patient's test result is normal, low, or high. These decision tools assist in one of the top goals in healthcare: timely communication.

I want to thank our committed reviewers of these tables; without them this important resource would not be available:

• The tables of critical limits and values were reviewed and updated by Gerald Kost, MD, PhD, MS, FADLM of the POCT•CTR, School of Medicine, UC Davis, and his UC Honors Program student team. A new glucose critical limits table is included this year based on their research in press, "Critical Limits and Clinical Recommendations for Notification of Life-Threatening Glucose Test Results in the 21st Century" in Archives of Pathology & Laboratory Medicine. 
• New this year, is Point-of-Care Testing Critical Limits by Kami Osher and Gerald J. Kost, MD, PhD, MS, FADLM, derived from their research published in Diagnostics (Basel) in 2026, "Critical Decision Thresholds for Urgent Physician Notification of Point-of-Care Testing Results."
• Also new this year is Critical Limits for Therapeutic Drug Levels, from research by Elina Kuang, Yasmeen Ibrahim, Kyle Cheng, and Gerald J. Kost, MD, PhD, MS, FADLM. "Drug Critical Limits for Urgent Physician Notification" was published this year in Clinical Pharmacology & Therapeutics (CPT).
• The cutoff concentrations for drug tests table was reviewed by Jason Hudson, PhD, Scientific Director & Laboratory Director at Quest Diagnostics. A callout for the DOT was added regarding the morphine 4000 ng/mL cutoff or testing for fentanyl not being approved yet. 
• The table of reference intervals was reviewed and updated by Sean T. Campbell, PhD, DABCC, FADLM, Clinical Biochemist, Mount Sinai Hospital, Toronto, ON.
• The pediatric reference intervals table was reviewed and updated by Khosrow Adeli, PhD, FCACB, DABCC, FADLM, Head, Clinical Biochemistry, Hospital for Sick Children and Principle Investigator – CALIPER Program, along with Erin Brady, MLO Managing Editor.

Lastly, I hope you enjoy reading “Preparing labs for the near future” by Erin Brady. Seven laboratory industry professionals provided their viewpoints on the changes they believe will have the largest impacts on labs over the next one to two years, such as artificial intelligence, automation, workflow redesigns, staffing challenges, and healthcare affordability and financial pressures.

We hope readers find this resource beneficial. For the online version of CLR, please visit www.clr-online.com.

For comments or feedback on CLR, please feel free to reach out to me at [email protected].