In my opinion, a physician is always trying to balance the clinical examination versus analytic diagnosis. Very helpful indeed in acute pathology, but as helpful in chronic cases. Always, the responsibility of a physician is to inform a patient what is necessary to confirm a serious diagnosis. In public health environment, it is necessary that institutions offer the best diagnosis media to their users. In private practice, a physician must be aware for the necessity of a expensive test, when in necessary and when is not. This is my perspective from the practice in México. In developed countries, this problem is not as limiting.

In my opinion, a physician is always trying to balance the clinical examination versus analytic diagnosis. Very helpful indeed in acute pathology, but as helpful in chronic cases. Always, the responsibility of a physician is to inform a patient what is necessary to confirm a serious diagnosis. In public health environment, it is necessary that institutions offer the best diagnosis media to their users. In private practice, a physician must be aware for the necessity of a expensive test, when in necessary and when is not. This is my perspective from the practice in México. In developed countries, this problem is not as limiting.

In general, chronic conditions are not defined by a single diagnostic test. In the case of chronic infections evaluation of serology along with viral markers (such as core antigen for HBV) and the immunologic status of the patient (i.e.CD4 cell counts) is more informative than a single test. As Dr. Lopez-Amador said, there should be also a balance between the cost-benefit of these diagnostic tools. It is really tempting to say that a quick diagnostic test will make a difference in public health, like the rapid HIV test. However, we must take in consideration that usually these rapid test are very sensitive but not very specific. Hence, they are not definitive.  Going back to the chronic conditions, I think that once the clinical condition is identified, it is better to determine at which stage the patient is and what is the disease activity, in order to start the propet treatment.

In terms of large epidemiological and health studies, an inexpensive and rapid test for selected chronic conditions - that perhaps is based on less invasive techniques, like fingerprick or saliva - would be very welcome and help to improve understanding of biases in self-report of chronic conditions.  "Point of care" devices/equipment is available - but currently, largely proprietary, expensive and with issues of reliability.  Innovations in use of smart phone technology is promising, but will take some time for scalability (see for example, http://intermountainhealthcare.org/hospitals/imed/about/news/releases/Pages/home.aspx?NewsID=1588 ).

While this would be helpful for screening (not necessarily diagnostic) in a population health research setting, a significant down-side would be the sensitivity and specificity of the test - specifically, the levels of false positives and false negatives.

Context is so important. In the past, Prof Kerin O'Dea competed for research funds to screen for chronic conditions in Aboriginal communities, and used WHO diagnostic criteria. This work identified cases of previously un-detected diabetes, and subsequently the Australian government saw the wisdom of funding Indigenous screening - adult health checks using standard pathology. Commercial point-of-care tests for HBA1c compared favorably with standard pathology in those days, regarding sensitivity and specificity for this aspect of chronic disease monitoring. (NB Be aware that my husband Kevin Rowley worked on this). In the Aboriginal Community-Controlled sector, we now have Aboriginal Health Workers specifically trained in point-of-care monitoring of HBA1c for clients with diabetes, and this is rebateable from Medicare. We find that this saves work in pursuing recalls, allows Doctors to order the test and receive the result and use the data to inform diabetes care in the one day, with less inconvenience to the client. I would not recommend it for diagnosis unless we knew how it performed in detecting pre-diabetes / impaired glucose tolerance. This is the perspective of a former pathology collector and practice manager.

Hi Marion, Absolutely - context is crucial.  The work you've done comparing results are also very important methodological steps (PoC results vs standard blood results).  Could you please point to results/publications/protocols?  With best, Paul 

In dermatology we can make a solid diagnosis through a  skin biopsy as a rapid test which might not be affordable in other branches of medicine.

A new publication that might contribute to this discussion.

Pinar Kuecuekbalaban, Silke Schmidt, Kathleen Kraft, Wolfgang Hoffmann, Holger Muelan. Exploring risks and benefits of point-of-care tests for healthcare and self-tests for laypersons: An interview study assessing complementary expert perspectives on diagnostic lab-on-a-chip systems. Technology and health care: official journal of the European Society for Engineering and Medicine (Impact Factor: 0.64). 10/2014; DOI: 10.3233/THC-140857

https://www.researchgate.net/publication/266973781_Exploring_risks_and_benefits_of_point-of-care_tests_for_healthcare_and_self-tests_for_laypersons_An_interview_study_assessing_complementary_expert_perspectives_on_diagnostic_lab-on-a-chip_systems

Article Exploring risks and benefits of point-of-care tests for heal...