This text guides readers in the process of utilizing tests and procedures to reach a correct diagnosis for their patients. Intended for learning and practicing members of a patient’s interdisciplinary care team, this guide provides information on how tests are performed, what results might be expected, and how medications can impact the diagnostic process. This chapter reviews the importance of the diagnostic process and how tests and procedures impact how medicine is practiced today. While the tests and procedures that are available are only increasing and providing more information, it is important to ensure that each medical procedure ordered is warranted and benefits the patient more than it causes harm.
So what is the diagnostic process? What does it entail?
A blank slate. That is how patients are considered early in a provider’s training. That is how the diagnostic process starts. Often, the first patients encounters early in training consist of walking into an exam room without knowing anything about the person on the other side of the door. From those early, tepid introductions, clinicians begin to hone their interview skills, advancing from asking the patient every medical question by rote, regardless of potential usefulness, to developing the sense of when and to whom to ask what questions. From there, a physical exam is performed. Once again, early on, the skill is taught in its entirety, and it subsequently develops into a more customizable approach as one’s experience grows. Only after the history and physical exam are complete does one dive into the realm of testing. Whether it is a screening blood test or confirmatory imaging, the diagnostic process seeks these tests as ancillary support to the gospel that is the history and physical exam.
That is how one is usually introduced to the idea of diagnostic testing and procedures: an adjunct to a complete history and physical exam, a tool or tools used to confirm or reject a list of potential diagnoses that one has developed on the basis of information gathered during a complete history and physical exam. In a patient with chest pain, radiographic imaging of the chest can confirm the diagnosis of suspected pneumonia, electrocardiogram changes can raise the suspicion of ischemia, or perhaps the absence of these changes can make gastroesophageal reflux more likely.
Once it is determined which appropriate tests or procedures the patient requires, the risks and benefits of completing the tests are discussed with the patient and consent is obtained. However, the clinician’s job is still not complete. A study published in the British Medical Journal found that while diagnostic errors are made in 10%–20% of all cases, even when the correct diagnosis is made, up to 45% of patients did not receive recommended evidence-based care. Additional considerations that might affect the potential tests the patient requires are a test’s positive and negative likelihood ratios, sensitivity, specificity, and positive and negative predictive values. See Chapter 3: Nuances and Characteristics of Tests for more details. This knowledge will help determine whether proposed laboratory tests, physical tests, or procedures will provide valuable or equivocal information. Additionally, when ordering tests for patients, it is important to not only have thought about how the process of completing the test will impact the patient’s life, but how the result may alter their future treatment plan as well. For example, if a biopsy may diagnose cancer, will the patient want treatment? If so, what treatment options are they eligible for? If the patient only wants to know the diagnosis and not receive treatment, is there a less invasive method to obtain the answer? Now, with the appropriate tests and procedures ordered, some of those blanks left over from the history and physical exam can be filled in, and that blank slate has emerged into a clearer picture of what the patient truly has.
The early years of training may be the last time that any practitioner sees a patient as a true blank slate. In this day and age of technology, informatics, and advancing testing, it is virtually unheard of to walk into a patient’s room knowing nothing. The electrocardiogram or chest X-ray is often performed and interpreted before any clinician says a word to a patient. Technology and electronic medical records help ensure that this information is available to any provider who sees a patient at a later date. Preemptively, this information can make practitioners susceptible to bias. For example, patients are often admitted from the emergency room with a diagnosis that does not later change despite availability of new information. This is often due to anchoring bias, as practitioners may become biased by the first diagnosis they hear. When test results are interpreted in such a way as to confirm one particular diagnosis, there is danger of making the wrong diagnosis due to framing bias. For example, a patient with anemia who recently traveled to Africa may be assumed to have malaria, and tests may only be ordered to confirm this suspicion while not ruling out other causes. If a test supports that anemia is present and the diagnosis is finalized, then it is likely to commit a type of bias known as premature closure. A systematic review found that autopsy results demonstrated the median misdiagnosis rate to be 23.5%. It is important to recognize the potential biases that can detract from obtaining the correct diagnosis and treatment plan.
In addition to the abundance of information available via advances in diagnostic testing, pharmaceutical treatments have developed drastically. Some days, it seems that polypharmacy, or use of five or more prescription medications, has become the rule rather than the exception. A study utilizing data from the National Social Life, Health, and Aging Project found that older patients were at most risk for polypharmacy. The prevalence of prescription medication use in older patients in the United States increased from 84.1% to 87.7% from 2005-2006 to 2010-2011. Polypharmacy also increased by almost 6% in the same time frame. A study utilizing the Canadian National Population Health Survey found that over 50% of older adults living in healthcare institutions are also affected by polypharmacy. The World Health Organization reported that 1/9 of the population is age 60 or older and this will likely increase to 1/5 in 2050, which suggests that the issue of polypharmacy will only become more relevant. To classify increasing polypharmacy as a positive or negative trend is not helpful, nor is the issue that simple, but what cannot be argued with is that polypharmacy is ever present.
Whether it is the ideal approach to our patients or not, clinicians often never see a blank slate. Polypharmacy and over-testing are ubiquitous in the current healthcare environment. Medicare expenditure on tests increased by 96%, other procedures by 82%, and imaging by 75% from 2000 to 2017, making these the largest portions of Medicare expenditure and the greatest growing areas of expenditure. Seeing patients deal with the effects of polypharmacy means seeing patients. Seeing patients with a handful of tests and procedures already ordered and performed means seeing patients.
As diagnostic tests and pharmaceutical treatments grow ever more complex, it behooves the astute clinician to become aware of how these areas influence one another. While the history and physical exam remain the most critical components of the diagnostic process, rarely are they enough. Part of applying the concept of the right test for the right patient means being aware of the impact of medications on these tests. Whether it is the rather obvious question of safety of blood thinners in invasive testing to the more nuanced questions of how steroids can affect a basic complete blood count and how one interprets a gastric emptying study in the setting of opioid use, it is essential to be aware of these questions and the impact medications have on various tests.
While this book serves as a guide for how medications can affect common tests, procedures, and the overall diagnostic process, nothing can replace what the provider adds to the care of the patient. Patients place great trust in healthcare professionals to study the information available, discuss the options with them, and help them make the best decisions. This book provides information to guide clinicians in making informed decisions. Importantly, it highlights the value of considering the diagnostic process as outlined above in efforts to best care for patients.