University of Virginia Health System

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LABORATORY MEDICINE UPDATE

March 4, 2005

Growth Hormone Reference Interval

Correction to the announcement of January 27, 2005: Nichols Institute Diagnostics, manufacturer of the human growth hormone reagent used in Medical Laboratories, has instituted a change in calibration that impacts the reference interval for this assay.  The new reagent is calibrated to the NIBSC 2nd IS 98/574 for Somatropin (recombinant DNA derived material).  The change in standardization was driven by World Health Organization (WHO) and will provide better consistency across different lots of reagents.  New reference interval is 0.1 – 16.8 ng/mL.

Change in Calculation of Mean Plasma Glucose from Hemoglobin A_1c Values

Based on recommendations from the American Diabetes Association (Diabetes Care 28, Supplement 1, January 2005), the calculation of Mean Plasma Glucose from hemoglobin A_1c values will change to one based on the study of Rohlfing, et al, (Diabetes Care 25:275-278, 2002) effective March 7, 2005.  The new calculation is based on the correlation of approximately 1500 comparisons using data from the Diabetes Control and Complications Trial (DCCT).  The formula for the conversion is:

MPG = (35.6*HgbA_1c) – 77.3

This value will be calculated only for hemoglobin A_1c values between 6.0% and 12.0% as this represents the range of data used to derive the above equation.  The table below provides a comparison of the values using the old and new calculation.