Need for calibration of medical devices in the health sector

By Joseph James, Senior Metrologist

In recent times, it has been observed that improvements on biomedical devices and systems used in diagnosis and treatment of illnesses have progressed parallel to the technological developments. However, the tendency of calibrating health equipment and other biomedical devices is still a puzzle. Although the consciousness and importance of calibration have reached to a remarkable point on some areas such as industry and trade in the past twenty years, the issue of calibration has started to be discussed in the past five years for the biomedical devices which are directly related to the health of human beings.

Diagnostic and treatment in the medical area are strictly tied to technological improvements and explores. Of course since the issue itself is human health, the improvement of the biomedical devices should be done under very high accuracy. The calibration for the biomedical devices which are measurement results that are linked to a common reference and are comparable across measurement systems, location, and time are essential for patient care, and disease prevention and control.

Benefits of calibration

Calibration has a myriad of benefits in the health sector. The milestone, of course, is reliable measurements. Accurate measurements play a vital role at each stage in development and production of quality medical services. The effectiveness of quality control steps depends directly on the accuracy and confidence with which the test and measuring instruments can yield test results. Thus systematic and periodic checking of test and measuring instruments is very essential for reliable measurements. Today’s global economy depends on reliable measurements and tests, which are trusted and accepted internationally.

Accuracy of the instrument readings is another benefit of calibration. Calibration provides how the medical devices can generate test results which are very close to the true value. Calibration is required to ensure monitoring data and that the reports are accurate, ensure continued process control and for safety of delivering treatment and diagnosis process of diseases. Both medical care providers and patients expect high quality service from every clinical laboratory. The most important gauge of quality is that the test results are accurate and suitable for medical practice. In fact, the various customers of clinical laboratories expect that all test results produced by all laboratories at all times are accurate and clinically meaningful.

Calibration also ensures that readings from the instrument are consistent with other measurements. The medical equipment/instruments used in hospitals for monitoring and treatment of patients require calibration in order to have confidence in their functioning and operation. Thus the laboratory test results provided from difference laboratories or difference medical devices are closely related.

Calibration also helps in establishing and demonstrating traceability. It is always essential that measurements represent the same quantity everywhere. This is possible only when the measurements have a common reference base, which is internationally accepted. This common reference base is the SI unit of measurement. Standard is the physical realization of the unit of measurement. The process of making sure that our measurement stem from a common reference base is termed as traceability.

Effects of poor measurements in medical services

Doctors need better measurements in order to diagnose illnesses, monitor patients and deliver treatments. Failure to ensure appropriate measurements will certainly have diverse effects.

Incorrect diagnosis of disease is one of the effects of poor measurements. Initial stage of disease diagnosis starts with laboratory testing of different samples from patients and finally the laboratory output is analytical data. This data is used in determining whether a patient has a disease or not. Medical equipment error tends to shift the test results above or below the true value detected by the medical devices. Therefore an error from equipment causes under-detection or over-detection of diseases.

Medical guidelines seldom contain any information about the performance characteristics for key tests used in the diagnostic decision process. Guidelines typically have specific thresholds or “acceptable ranges,” such as 8.9 to 10.1 mg/dL of calcium in tests to diagnose hypercalcemia. If the equipment has an error of ±1.0 mg/dL, a result of 9.5 mg/dL may be altered to 8.5 mg/dL which is under-detection of the disease, or 10.5 mg/dL which is over-detection of the disease.

Likewise, non-calibrated equipment used in testing the patients sample can contribute to alter patient treatment. Medical doctors rely on the clinical results obtained from the laboratory. If the result is incorrect, it might cause the doctor to under-dose or over-dose the patient. An error in medical instruments/equipment like clinical thermometers (body temperature), sphygmomanometers (blood pressure), tonometer (intraocular pressure), spirometer (respiratory diseases), weighing scales (body weight), syringes etc. can cause medical decision making to alter from the normal decision. Take an example of the measurement of paediatric drug dose. Cups to measure paediatric liquid medication doses (2.5 ml and 5ml) commonly sold with over-counter-medications, if marked incorrectly delivered volumes may be under- or over-volumes specified, hence under- or over-dose of the infants. Another example can be the mass of drugs (250 mg, 500 mg). An error in mass of drugs may contribute to patients’ problem. In another scenario, a testing instrument may indicate incorrect test results which can alter the patient’s treatment as compared with absolute thresholds. Medical errors caused by calibration error might contribute to patients suffering permanent or temporary disability and even cause death.

But non-calibration of medical equipment can also contribute to increased health costs. A patient who has been incorrectly diagnosed to have a certain disease will incur costs for medication and follow-up for treatment. Analytical bias affects health care costs by increasing the number of follow-up tests. Analytical bias of 0.1 mg/dl may cause increased health care cost. An important effect of calibration error on clinical outcome is in detection of disease, particularly when threshold values are used for diagnosis.

The bottom-line

Calibration in the medical sector is a paramount practice in improving public health. Unfortunately, there still remain many problems of comparability in hospital measurements not only at the national and international levels, but also between and within hospitals. The resolution of these problems would lead to immediate improvements in health care as well as to considerable cost savings.