Effective Tuesday, November 26, 2013, the University of Iowa Hospitals and Clinics core laboratory will change the adult reference ranges for five chemistry assays:

Test	Epic #	Previous Range	New Range
ALANINE AMINOTRANSFERASE (ALT)	LAB132	0 – 35 U/L Males 0 – 20 U/L Females	0 – 41 U/L Males 0 – 33 U/L Females
ASPARTATE AMINOTRANSFERASE (AST)	LAB131	0 – 37 U/L Males 0 – 31 U/L Females	0 – 40 U/L Males 0 – 32 U/L Females
THYROXINE – FREE (FREE T4)	LAB127	0.92 – 1.57 ng/dL	0.90 – 1.70 ng/dL
CALCIUM-URINE 24 HR	LAB580	15 – 150 mg/24 hr	No range for normal / abnormal flagging
VITAMIN B12	LAB67	243 – 894 pg/mL	211 – 946 pg/mL

• The changes in AST, Free T4, and vitamin B12 are to adjust to new methodology from switch to new chemistry analyzers in the core laboratory.  These ranges are from the package inserts of the FDA-approved assays.


• The change in ALT reference range is a more significant shift.  The previous range, which is significantly narrower than the range used by many other institutions and commercial laboratories, was from a normal range study performed 20 years ago at Iowa.  Over the years, this tight range is flagging a high percentage of patients as abnormal.  Currently, 51% of adult females tested in the core laboratory are flagging abnormal for ALT.  While this tight range may help identify subclinical liver disease (e.g., early non-alcoholic steatohepatitis), it may also drive anxiety and downstream procedures.  However, to provide awareness of the “borderline” abnormal range of ALT that has increased risk of subclinical liver disease, the following comment will be appended to ALT results:
  
  "The upper limit of normal for alanine aminotransferase (ALT) reference ranges for adults is controversial with some authorities recommending limits as low as 30 U/L for males and 19 U/L for females.  There is increased incidence of subclinical liver disease (e.g., early steatohepatitis) in patients with ALT values in the range of 31-41 U/L for males and 20-33 U/L for females.  ALT values should always be interpreted in conjunction with clinical history, physical examination findings, and, if applicable, data from other diagnostic tests."


• The change to 24 hr urine calcium is to turn off normal/abnormal flagging given that differences in diet and other factors influence calcium excretion and thus the expected range. The following comment will be appended to results:
  
  "24-Hour urinary calcium concentrations vary with amount of calcium in diet.
        Calcium-free diet: 5-40 mg Ca/day in urine
        Low to average calcium intake (up to 800 mg/day): 50-300 mg Ca/day in urine
        High calcium diet (800 mg/day or more): > 250 mg Ca/day in urine"

Questions should be directed to Matthew Krasowski, MD, PhD, medical director of the Clinical Chemistry (384-9380, matthew-krasowski@uiowa.edu).