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Purpose of investigation: Difference between revisions
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When one orders a test (laboratory, imaging, or otherwise), it's important to have a predetermined purpose for the test and not just ordering tests willy-nilly. Generally, investigations can be used for: | '''Clinical decision-making''' refers to the process of deciding how to select clinical decisions. This is important when considering whether to perform a test or not. | ||
== Purpose of investigation == | |||
When one orders a test (laboratory, imaging, or otherwise), it's important to have a predetermined purpose for the test and not just ordering tests willy-nilly. Tests are often invasive as well as time-consuming and expensive, and so they should be worth the risk, time, and expense. There is no point in ordering a test if the test result does not influence how you approach the patient. | |||
Generally, investigations can be used for: | |||
* Screening (healthy or not healthy) | * Screening (healthy or not healthy) | ||
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An investigation should have some form of value for the patient (except if done in a research setting or for epidemiological purpose, in which case the investigation has value for researchers, and in turn, future patients). The value to the patient should also weigh up for any negative consequences of the investigation. | An investigation should have some form of value for the patient (except if done in a research setting or for epidemiological purpose, in which case the investigation has value for researchers, and in turn, future patients). The value to the patient should also weigh up for any negative consequences of the investigation. | ||
=== Frail patients === | |||
Many frail patients, especially elderly, cannot or do not want to undergo certain tests or invasive procedures. Is there, for example, a point in evaluating a frail elderly person for cancer, if they do not want to or cannot undergo cancer treatment anyway? Take the following example: | |||
A frail elderly patient living in an institution (like a nursing home) has a positive faecal occult blood test. The physician considers to refer them to colonoscopy, but stops to consider: how will a colonoscopy be of value to the patient? In their current state, even if the colonoscopy would show colorectal cancer, the patient would not be a candidate for any anticancer surgery or chemotherapy, so even if a diagnosis is made, nothing will change for the patient (except the stress of knowing they have cancer). In addition, colonoscopy is an invasive investigation which requires strict patient preparation, which can be difficult for a frail elderly to perform or even survive. | |||
If they have colorectal cancer and it grows and eventually causes intestinal obstruction, colonoscopy may be indicated for stenting the bowel, in which case the colonoscopy would have value for the patient as palliative therapy | |||
One can also argue that even performing a faecal occult blood test in this case has no value for the patient, because the next step after a positive test would be a colonoscopy, a procedure which would not be of value to the patient anyway | |||
=== Patient management is the same regardless of test result === | |||
In some cases, it may be temping to order an investigation to gain more information, but it's important to consider whether that information is of value or not. Take the following example: | |||
A young male has had back pain for a few days. The pain is not severe, and there are no red flags for cauda equina syndrome. He wants an MRI to know what's going on, but the physician stops to consider: how will an MRI be of value to the patient? The patient may or may not have a herniated disc, but even if they do, a herniated disk without red flags isn't an indication for surgery anyway. As such, whether the MRI shows a herniated disc or not, the management will be the same (no surgery, only physical therapy and pain relief), and the MRI is therefore of no value to the patient (and it is resource-intensive) | |||
On the other hand, if the patient has debilitating pain or there are red flags present, he may have cauda equina syndrome, in which case surgery is indicated. In this case, MRI has value: it determines whether they need surgery or not | |||
Another example: | |||
A middle aged woman has symptoms of an upper respiratory tract infection. After taking the anamnesis and physical examination, you're certain that it's a viral infection. You reflexively want to order a CRP or leukocyte count, but you stop to consider: will the laboratory investigation likely be of value to the patient? You know that viral URTIs only cause mildly elevated inflammatory parametres, so that's likely what you'll find anyway. And even if the CRP is higher than you expect, you're certain enough that this is not a bacterial infection, so you won't be administering antibiotics anyway. So even after making the investigation, you'll most likely not be changing your management of this patient; managing their symptoms and encouraging rest, without antibiotics | |||
On the other hand, if the patient has symptoms which make it difficult to distinguish between viral and bacterial infection clinically, a laboratory investingation is merited, as it provides additional information which can aid in the diagnosis and therefore the treatment in this case | |||
Consider that many laboratories can analyse a pharyngeal swab for specific airway viruses. Would making such an investigation in this case change the management of the patient? In most cases no, as there is no specific treatment for most airway viruses anyway. | |||
== Screening == | == Screening == | ||