An introduction to diagnostics

What are diagnostics?

Diagnostics (medical tests) are means to reach a diagnosis and determine patients’ suitability for therapy or disease monitoring.

When are they used?

There are many important forms and fields of diagnostics in medicine e.g. medical imaging, microbiology, virology, biochemistry, serology, immunology, haematology, genetics etc.

In some cases, diagnostics can identify a condition before it is clinically apparent; for example, screening for diabetes in an asymptomatic individual.

Diagnostics in medical practice

Using diagnostics in medical practice traditionally includes a number of steps including test selection, based on clinical picture or screening in the right patient, test ordering, sample collection, sample transportation to a laboratory, sample preparation, sample analysis, result reporting, result interpretation and clinical action.

More recently, some of these traditional steps have been omitted with the emergence of rapid diagnostic tests (RDTs) and their use in clinical practice.

The aim of RDTs

The aim of RDTs is to provide actionable information for patient care in a timely manner, ideally at the time and location of the patient’s interaction with health care systems.

RDTs (often referred to as point-of-care tests (POCT)) when deployed near-patient are often simple to use and therefore can offer diagnostic support away from more sophisticated diagnostic laboratory support, for example in primary care.

Development, verification, and validation

Development, verification, and validation as well as training personnel for testing and interpretation are critical for establishing the performance characteristics of diagnostics.

In-vitro diagnostics in infection make it possible to identify organisms causing an infectious disease and to perform antibiotic susceptibility testing to prescribe targeted treatments.

The benefits of diagnostics

Diagnostics can benefit from the use of antimicrobial stewardship and infection prevention measures, e.g. diagnosing COVID-19 with a rapid polymerase chain reaction (PCR).

These measures not only help inpatient management but also in applying or continuing strict infection control measures to prevent further or ongoing spread. Overall, if they are used appropriately, diagnostics can benefit individuals, public health and improve costs to the healthcare systems.

Misusing diagnostics

Misusing diagnostics can cause harm to patients and can lead to unnecessary interventions and increased cost of care. Hence if a test is not indicated for a patient, then it shouldn’t be requested.

If the requester is not sure how a test is used, then they should seek further advice or guidance from other experts prior to requesting, in order to have a greater chance of potential use of a diagnostic test and subsequently of improving patient care.