Medical labs and pathologist

Dr AN Pendharkar

The role of pathology laboratories in healthcare and management of patients is undisputed but sadly are not given their due importance. The reasons are many fold but the root cause appears to be the diminishing role of pathologist as a key person in the laboratory. I am sure, this opening statement of mine will create various opinions contrary to the view and criticisms from certain sections who feel that laboratory medicine is only performing tests with various technologies available.

Nothing can be farther from the truth. It should be remembered that the basic concept is that each specimen in the laboratory is considered as a patient and utmost care should be taken in handling the samples.

The results generated are correlated with the clinical condition that requires basic knowledge of medicine and profound knowledge of the subject pathology.

It may appear puerile but if you analyse certain basic errors committed by the laboratories while putting their names, the commonest being “pathological lab”, means the lab is abnormal. It will surprise many when the persons running the “labs” will give various and erroneous meaning of the word “pathology”. Hence other names like clinical lab appears to be more appropriate and convenient.

The recent trend of grouping all medical labs and calling it “laboratory medicine” is in vogue. The presence of the word medicine signifies that a medical background is a must and is best provided by a “pathologist”. Here the misconcept of pathologist being a person who runs a pathology lab should be emphatically cleared. Pathologist is a person who has obtained a post graduate degree in the subject pathology .

The role of pathologist in labs for clinical chemistry and serology tests is challenged by some regarding the technical aspect. This arises from the fact that during post graduate training, pathologists are not given to perform routine tests in the hospitals. As post graduate students the emphasis is on histopathology, hematology and autopsy techniques and why not? Since these investigations help to learn the pathology and pathogenesis of the disease and needs expertise. Clinical pathology and clinical chemistry techniques change very fast and there is a constant influx of sophisticated equipment and advanced techniques. Emphasis is more on interpretation and clinicopathologic correlation. The utility of sophistication, variety and availability of lab tests continue to grow along with clinician’s dependence on such tests. Newer technologies such as monoclonal antibodies, DNA probe, PCR , specific hormone assays, immunochemical, cytochemical staining and flow cytometry have markedly improved the accuracy and diagnostic value of many tests .

Having said this the old saying remains, ‘man has made the computer and not the other way’.

It is a sad state that most of the pathologists in private practice refrain from interpreting the results, due to lack of feedback regarding the clinical history and treatment of patient and further it does not go down well with the clinicians as it may sometimes differ with their opinion. This has lead to mechanical approach to investigations by pathologists, though the role of pathologists for histopathology and cytology is undisputed.

Manual errors are inevitable and it is impossible to eliminate all the errors. But a realistic approach is to detect them and strive to reduce them. With the detection of errors it is possible to identify their source, causes and ways to prevent them. Systematic errors can be identified and eliminated with utilisation of quality control techniques. Role of pathologist in implementing the above is of paramount importance. Other responsibilities that lie with the pathologist are critical selection of methods, reagent and instrumentation to ensure accuracy, precision, specificity and delineation of normal values. It should be remembered that good quality is the result of continued effort and can not be achieved without paying the price for it. A comprehensive quality control system may increase the overall costs as much as 10 per cent but it’s the best possible investment.

The comprehensive quality control programme should include:

• standard reference solutions for analysis,
  
• serum controls should be determined with each batch of analyses
  
• random unknown specimens may be split and checked as duplicate analysis and evaluated daily
  
• assayed specimen or unknown from interlaboratory program should be periodically analysed with patient’s specimens. This will assure accuracy of determination.

The values obtained on controls should be recorded as a monthly quality control sheet and plotted as a Levy Jennings type chart.

Pathologist is aware of the fact that considerable variations in the results is due not only to instrumentation, methodology and other lab techniques but also to more subtle pre-analytical factors such as position or condition of patient, time of the day, age, sex, climate, effect of diet or drugs and characteristic of test population. It is therefore imperative that reference ranges from labs be obtained by the clinicians to be determined by the lab for its own procedures, patient population etc.

General principles for interpreting lab tests:

Under the best circumstances no test is perfect {e.g. 100 per cent sensitivity, specificity predictive values} Any particular lab result may be incorrect for a large variety of reasons regardless of the high quality of lab . The greater the degree of abnormality of the test result, the more likely that a confirmed abnormality is significant or represents a real disorder. multiple test abnormalities are more likely to be significant than single test abnormality.

When two or more tests for the same disorder are positive, the results enforce the diagnosis but when only one test is positive and others are not, the strength of interpretation is diluted.

Excessive repetition of tests is wasteful and excess burden increases the possibility of lab errors. Tests should only be performed if they will alter a patient’s diagnosis, prognosis, treatment or management. Incorrect test values or isolated individual variation in results may cause “Ulysses syndrome” and results in loss of money and peace of mind. Reference ranges vary from one lab to other. These normal ranges represent collected statistical data, rather than classification of patients as having disease or being healthy. The effect of drug on lab test values must never be overlooked. Vitamin C may produce a false negative test for occult blood in stool.

To conclude, it can be said that inspite of having a stringent quality control system in place and best of available equipment, errors do occur.

It is at this stage and for these reasons, that a person having the required knowledge of the subject understand, correlate various factors and arrive at the correct results. These are present in a pathologist.

The writer is honorary secretary of Association of Practicing Pathologists of India.

Email: kartikpendharkar@yahoo.com