PURPOSE OF A DIAGNOSTIC LABORATORY

1. PURPOSE OF A DIAGNOSTIC LABORATORY
Dr.T.V.Rao MD
Today we have many Institutes and Medical Colleges, who train the Medical personal for advancement of education for awarding MD Degrees, already many finding underemployment and unemployment, The reasons can be many we failed to translate our knowledge to the benefit of patients, Almost many Medical colleges are set up with an idea of profit and least inputs in Academics and research, it is not alone the system the Physicians many times fish the diagnosis without knowing the purpose of a Diagnostic test, Nobody educated on this matter to treating doctors and clinical Microbiologists, The clinicians should know when to order a Test Ordering and interpreting diagnostic tests are fundamental skills which the treating physicians should know or else it is an empirical diagnosis with drain of resources without purpose . Surprisingly, however, evidence indicates that many of us are poorly trained in this vital area. Studies have shown that physicians commonly order more laboratory tests than required, use them for the wrong purposes, (KICK BACKS) and ignore or misinterpret their results. While these errors have obvious implications for the quality of patient care, there are large socioeconomic implications as well. When we were studying Text book of microbiology we learnt to words in Immunology and Antigen Antibody reactions 1 Sensitivity and 2 Specificity, if we know these two words in depth, it is a great foundation to Laboratory Medicine, and the sensitivity of a test refers to the proportion of patients with a given disease who have a positive test. The specificity of a test refers to the proportion of patients without the disease who have a negative test. Predictive value, on the other hand, refers to the likelihood that a patient has or does not have the disease, given positive or negative test result, the purposes for which tests are obtained have a great dealt do with both the choice of diagnostic test and its interpretation.* One survey of physicians in a large teaching hospital found that three general reasons accounted for most laboratory test ordering: diagnosis (37%), monitoring therapy (33%), and screening for asymptomatic disease (32%).The Microbiologists and Physicians should know how the diagnosis helps to be positive in a large proportion of patients with the disease (high sensitivity) and negative in a large proportion without the disease (high specificity). Ideally, for the test to be maximally useful for diagnostic use, both sensitivity and specificity should be 100%. This would mean that every patient with the disease would have a positive test (no false negatives) and result in a negative predictive value of 100% .Similarly, positive tests would occur only in patients with disease (no false positives), resulting in a positive predictive value of 100% . Unfortunately, tests with such high sensitivity, specificity, and predictive value are unheard of, In fact, tests with high sensitivity tend to have low specificity, and vice versa. A little thought, however, will allow you to choose the proper test for your particular diagnostic purpose. Never forget the cost of Medical treatment increased with ignorance and doing irrelevant investigations much of the costly tests, misuse and misinterpretation of diagnostic tests is due to the fact that physicians are not always able to manage intuitively the probabilistic information that most laboratory tests provide. The diagnostic process is one of successive probability revision. Knowledge of the operating characteristics of laboratory tests (i .e. sensitivity, specificity, and predictive value) can greatly facilitate this process .Knowledgeable use of these operating characteristics allows test choices to be tailored to the specific purposes of diagnosis, monitoring, and screening. In addition, such use allows proper interpretation of normal test results, as well as discriminate use of common strategies such as screening, rule-out testing, repeating tests, and combination testing. I am bold to confess the many times the treating physicians do not put thought when ordering the test, and leave alone what it means if it is negative or positive, Most of the Times the reasons to investigation are not scientific, and in this process no competent laboratory specialist can interpret tests. The conditions are no better in Teaching

2. hospitals may be worse all matters are left to House surgeons and trainee nurses, Never forget the laboratories are fishing places the professionally run laboratory will support your scientific diagnosis rest is a Trial and error on human guinea pigs ? After having qualified specialists there will few details on requisition form to guide the laboratory – THE GREAT QUESTION CAN WE IMPROVE OR LABORATORIES? FISHING FOR DIAGNOSIS IN LABORATORIES CAN BE DANGEROUS?
*Ref Use of the Laboratory CRAIG KAPLAN and Google image resource
Dr.T.V.Rao MD Professor of Microbiology Freelance Writer