Calibration Errors in Testing Raise Healthcare Costs

Measurement uncertainties in clinical laboratory tests can greatly increase the cost of healthcare, according to a new study commissioned by the U.S. National Institute of Standards and Technology (NIST, Gaithersburg, MD, USA).

The study estimates that calibration errors in measurements of calcium levels in blood, for example, may add U.S.$60-199 million in annual healthcare costs. High calcium levels can be a symptom of cancer or thyroid disorder. Accurate measurements are critical because calcium levels in healthy people fall within a narrow range, 8.9-10.1 mg/dl.

Following interviews with laboratory managers and equipment manufacturers, researchers estimated that results for up to 15% of calcium lab tests contain calibration errors of 0.1-0.5 mg/dl. This means that some results that fall in the center of the normal range, such as 9.7 mg/dl, may be for patients with elevated calcium, defined as 10.2 mg/dl and above, who will receive no follow-up. On the other hand, patients with values above the threshold who actually have normal calcium levels may receive unnecessary follow-up, such as hormone measurements and chest x-rays.

The study analyzed data for more than 89,000 patients receiving serum calcium tests at the Mayo Clinic (Rochester, MN, USA) and found that calibration errors added $8-89 per patient to the healthcare of about 3.5 million patients. The study was conducted by researchers from the Mayo Clinic and the Research Triangle Institute (RTI, Research Triangle Park, NC, USA). Major sources of calibration errors include differences in analysis methods used by different laboratory instruments, lot-to-lot variations in calibration materials, and lack of "traceability” between secondary reference materials and primary standards, noted the researchers.





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National Institute of Standards and Technology (NIST)