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Archimedes
Towards evidence based medicine for paediatricians Edited by Bob Phillips When a test isn’t a test There are many reasons why we request tests, in medicine. One imaginary patient’s journey picks up a number of them. Take a patient who presents with a painless lump on their arm, who’s tired and a bit pale and washed out. You might send a series of blood tests, including a full blood count to diagnose anaemia. You may also request an ultrasound of the lump, which may show an ugly mass with features consistent with sarcoma. Your friendly local plastic sarcoma surgeon might do a biopsy for you after an MRI, and the histopathologists confirm it’s a rhabdomyosarcoma. All these tests are aimed at making a diagnosis: to clarify if the patient in front of us has, or does not have, the condition. The oncologist who then takes up the patient’s care will move to undertake a series of further investigations; bone or positron emission tomography scanning, marrow biopsies and CT chest. These scans are not to make the diagnosis—that’s known—but to locate the disease, explore it’s extent and ultimately come up with a risk-stratification which may inform prognosis, affect choice of treatment, or both. Should the disease be metastatic, treatment will include anthracyclines. This group of chemotherapy agents will mean the patient is subject to repeated echocardiography, looking for early signs of drug-induced cardiomyopathy. Here, the test is used to monitor function to assess for the development of a condition. In those who present very young with a distinct subtype of rhabdomyosarcoma may now also be offered gene testing for a cancer predisposition syndrome: in this situation, the patient is being screened to highlight a potentially relevant issue for their future. The ways we look to appraise a test vary according to its use: a test to diagnose may be appraised for its accuracy; a test to stratify risk, by its ability to predict outcomes and the separation of the risk groups; a monitoring test by its ability to change management and prevent adverse consequences developing; and a screening test by both the accuracy of the test itself and the interventions that can ameliorate anything discovered. (There are then also those tests we do to make ourselves feel better. Like the chest X-ray when we’re going to give a short course of amoxicillin regardless of what the picture shows…) Bob Phillips Correspondence to Dr Bob Phillips, Centre for Reviews and Dissemination, University of York, York YO10 5DD, UK; [email protected] Competing interests None. Provenance and peer review Commissioned; internally peer reviewed. Accepted 24 August 2014
▸ http://dx.doi.org/10.1136/archdischild-2014-306689 ▸ http://dx.doi.org/10.1136/archdischild-2014-306159 Arch Dis Child 2014;99:958. doi:10.1136/archdischild-2014-307382
958
Arch Dis Child October 2014 Vol 99 No 10
Downloaded from http://adc.bmj.com/ on June 21, 2015 - Published by group.bmj.com
Towards evidence based medicine for paediatricians Bob Phillips Arch Dis Child 2014 99: 958
doi: 10.1136/archdischild-2014-307382 Updated information and services can be found at: http://adc.bmj.com/content/99/10/958.2
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Articles on similar topics can be found in the following collections ADC Archimedes (212) Oncology (710) Pathology (212) Clinical diagnostic tests (1042) Radiology (899) Surgery (261) Surgical diagnostic tests (249) Screening (epidemiology) (505) Screening (public health) (505) Competing interests (ethics) (156) Drugs: cardiovascular system (482) Drugs: infectious diseases (883) Echocardiography (133) Journalology (208) Radiology (diagnostics) (716)
Notes
To request permissions go to: http://group.bmj.com/group/rights-licensing/permissions To order reprints go to: http://journals.bmj.com/cgi/reprintform To subscribe to BMJ go to: http://group.bmj.com/subscribe/
Archimedes
Towards evidence based medicine for paediatricians Edited by Bob Phillips When a test isn’t a test There are many reasons why we request tests, in medicine. One imaginary patient’s journey picks up a number of them. Take a patient who presents with a painless lump on their arm, who’s tired and a bit pale and washed out. You might send a series of blood tests, including a full blood count to diagnose anaemia. You may also request an ultrasound of the lump, which may show an ugly mass with features consistent with sarcoma. Your friendly local plastic sarcoma surgeon might do a biopsy for you after an MRI, and the histopathologists confirm it’s a rhabdomyosarcoma. All these tests are aimed at making a diagnosis: to clarify if the patient in front of us has, or does not have, the condition. The oncologist who then takes up the patient’s care will move to undertake a series of further investigations; bone or positron emission tomography scanning, marrow biopsies and CT chest. These scans are not to make the diagnosis—that’s known—but to locate the disease, explore it’s extent and ultimately come up with a risk-stratification which may inform prognosis, affect choice of treatment, or both. Should the disease be metastatic, treatment will include anthracyclines. This group of chemotherapy agents will mean the patient is subject to repeated echocardiography, looking for early signs of drug-induced cardiomyopathy. Here, the test is used to monitor function to assess for the development of a condition. In those who present very young with a distinct subtype of rhabdomyosarcoma may now also be offered gene testing for a cancer predisposition syndrome: in this situation, the patient is being screened to highlight a potentially relevant issue for their future. The ways we look to appraise a test vary according to its use: a test to diagnose may be appraised for its accuracy; a test to stratify risk, by its ability to predict outcomes and the separation of the risk groups; a monitoring test by its ability to change management and prevent adverse consequences developing; and a screening test by both the accuracy of the test itself and the interventions that can ameliorate anything discovered. (There are then also those tests we do to make ourselves feel better. Like the chest X-ray when we’re going to give a short course of amoxicillin regardless of what the picture shows…) Bob Phillips Correspondence to Dr Bob Phillips, Centre for Reviews and Dissemination, University of York, York YO10 5DD, UK; [email protected] Competing interests None. Provenance and peer review Commissioned; internally peer reviewed. Accepted 24 August 2014
▸ http://dx.doi.org/10.1136/archdischild-2014-306689 ▸ http://dx.doi.org/10.1136/archdischild-2014-306159 Arch Dis Child 2014;99:958. doi:10.1136/archdischild-2014-307382
958
Arch Dis Child October 2014 Vol 99 No 10
Downloaded from http://adc.bmj.com/ on June 21, 2015 - Published by group.bmj.com
Towards evidence based medicine for paediatricians Bob Phillips Arch Dis Child 2014 99: 958
doi: 10.1136/archdischild-2014-307382 Updated information and services can be found at: http://adc.bmj.com/content/99/10/958.2
These include:
Email alerting service
Topic Collections
Receive free email alerts when new articles cite this article. Sign up in the box at the top right corner of the online article.
Articles on similar topics can be found in the following collections ADC Archimedes (212) Oncology (710) Pathology (212) Clinical diagnostic tests (1042) Radiology (899) Surgery (261) Surgical diagnostic tests (249) Screening (epidemiology) (505) Screening (public health) (505) Competing interests (ethics) (156) Drugs: cardiovascular system (482) Drugs: infectious diseases (883) Echocardiography (133) Journalology (208) Radiology (diagnostics) (716)
Notes
To request permissions go to: http://group.bmj.com/group/rights-licensing/permissions To order reprints go to: http://journals.bmj.com/cgi/reprintform To subscribe to BMJ go to: http://group.bmj.com/subscribe/
