Tuesday, February 17, 2015

Medical instruments; need for standards, calibration and checking

It is a common experience these days, that whenever we go and consult a medical practitioner, he usually suggests number of investigative pathological tests involving blood or urine analysis, scans like X ray or MR besides ECG using an electrocardiograph. There is always a debate, whether these are are really required or not in case of each and every patient, but let us keep that controversy to a side.
Most of these test are done by specialized pathological laboratories, who collect your blood or urine samples and give you a report, indicating the values of blood or urine constituents in some form of units, unknown to a layman. Fortunately they also give the high and low limits, within which these values must exist for a normal person, indicating if there is any abnormality.

Use of other types of medical instruments also has become very common. These range includes simple instruments for blood pressure checking, blood sugar checking, which are used by individuals, to complex scanners and monitors used in hospitals. .

I have been often wondering about accuracy of the results obtained from these instruments as there have been many instances, where results for the same test from two different laboratories are found to be differing widely. This should not really come as a surprise or something that is totally unexpected, as almost all analytical instruments are always of comparison type, meaning that they would compare a specimen against a standard specimen and indicate the variation in percentage terms and their accuracy depends upon the standard, used in the measurement.

The process of setting up such an analytical instrument, usually involves a step called standardization or calibration. In this process, the instrument is set to zero or some other value using a standard specimen for measurement. It should be obvious that the accuracy of reading of an analytical instrument actually depends upon how accurately the calibration has been done and the genuineness of the standard.

The calibration process is not something that is needed only for medical or pathological instruments. Every measuring instrument needs this process to set it up. Let us consider the simplest of all measuring instruments like a measuring tape or a scale or a simple weighing instrument like a balance. The markings on a measuring tape or a scale tell us the length of an object, but how do we guarantee that the reading obtained from a measuring tape or a scale is correct? Similarly, we note weights of objects by comparing them with standard weights that are put in other pan of the balance. But how do we guarantee that these weights, we use for comparison, are of correct weight?

To ensure this, each country maintains standards of length, weight etc, which are again compared with International standards. In India, such standards of length and weight and maintained by national Physical laboratory (NPL) in Delhi and each every manufacturer of measuring instruments is expected to have his own standards, which have been verified and compared to NPL standards.

Coming back to the medical and pathological instruments, which tell us about blood or urine constituents; it is easy to see the need for calibrating these instruments against standards by a statutory body, which can certify that the instrument is calibrated and accurate. Unfortunately, India does not have a single nationally recognized medical device testing laboratory. The Drugs and cosmetics act has no regulatory provisions regarding standards. India has regulatory mechanisms for the pharmaceuticals industry but none for the medical instruments industry.

India imports about 70 to 75% of its medical instruments requirements with balance being locally manufactured in states of Haryana, Noida (UP) and Gujarat. The Government has now decided to set up three medical device testing laboratories in these places.

In a first step towards recognizing medical devices as an industry separate from the pharmaceuticals industry and requiring different regulatory standards, the commerce ministry has decided to fund the setting up of three medical device testing laboratories in Noida (UP), Haryana and Gujarat, which already have device manufacturing clusters.

I think that it is an extremely positive step, which when functional, would be able to enthuse little more confidence in the hearts of the patients that the reports received by them are accurate and they have not been taken for a ride.

17th February 2015

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