What’s the purpose of a diagnostic test?

  • Posted on 26.10.2012

What’s the purpose of a diagnostic test?

Lluís Bohígas Santasusagna

Lluís Bohígas Santasusagna

Director, Institutional Relations, Roche Diagnostics


In vitro diagnostic (IVD) tests are likely to be a part of everyone’s life, in many cases, more than once. Yet most people do not know what these tests are or what they do.

Conducted on a sample of blood, urine, stool or tissue, IVDs assess whether a person has a specific condition, biomarker or genetic predisposition. They are often conducted away from the patient in clinical laboratories, which makes them less visible and their role less well known. But this too is changing as more and more tests are being created for at-home use. From pregnancy tests to diabetes monitors, in vitro diagnostics are empowering patients’ with information about their health and giving doctors the tools that they need to choose optimal treatments for the people in their care.

For the purpose of diagnosing, monitoring, screening and prognosis, in vitro diagnostic tests are essential at every step. 

  • Diagnosis is the process of finding out if a patient has a specific disease. A medical professional prescribes a test to make a diagnosis or to exclude possible illness. The clinical course in the first case will be to implement appropriate treatment for the diagnosed disease, while in the second case – other diagnostic tests have to be pursued. For some diseases, it is not only important to know what the nature of the disease is but also the degree of development. Doctors may need to be aware of the stage of the disease, its progresses, whether it is stable or in regression. Likewise, diagnostic tests also allow doctors to assess whether the chosen treatment is effective in stopping the progression of the disease, a method that has already been commonly used in the treatment of cancer.
  • Monitoring intends to see if the disease is controlled, a purpose that is very common in chronic diseases such as diabetes. Chronic diseases cannot be cured, but patients can avoid getting worse through the use of medications, hormones, or lifestyle changes. Monitoring allows for the control of such diseases.
  • Screening consists of studying patients who do not yet present any signs or symptoms of a specific illness in order to find out if it has begun to quietly develop and if so, to be able to apply treatment as soon as possible. These tests are applied to large segments of the population and should therefore be simple and cheap. Their primary purpose is not so much diagnosing a disease, but rather identifying those people that may have it.
  • Prognosis allows clinicians to assess the likelihood a patient has for developing a disease in the future and therefore take precautions earlier rather than later. Genetic tests, for example, analyse a patient’s predisposition for developing a disease, allowing the patient and doctor to be more attentive to discovering early signs of the disease and to take preventive measures as needed.

Beyond these purposes of diagnostic tests, it’s important to know that they do not treat patients or cure illnesses, but are an integral step toward both.  They do not come into direct contact with the patient as they only need a sample from the patient to produce results. The impact of these results on healthcare decisions is significant and vital, though it also relies on a medical professional’s accurate judgement and appropriate choice of treatment. In vitro diagnostic tests serve as a guide providing essential information on health and the care of it.

– Lluís Bohígas Santasusagna, Director of Institutional Relations, Roche Diagnostics

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