A cardinal sign is a key diagnostic indicator of disease. Conditions may have one or more sign clinicians can use to recognize them and make a diagnosis in preparation for developing a treatment plan. Medical professionals learn about various cardinal signs in training and develop the skills they need to identify and assess them through clinical practice. Experience can allow someone to identify a sign that may not be obvious, or could be masked by another symptom.
For example, inflammation has several cardinal signs which point to a definitive diagnosis. An area of inflamed tissue should be red, swollen, hot to the touch, painful, and less functional. If a patient reports with these symptoms, a care provider can diagnose inflammation and offer some recommendations on treatment, like icing and medication. Another condition with easily identified cardinal signs is Parkinson’s disease, which presents as a resting tremor with rigidity, slow movement, and trouble balancing.
In a clinical evaluation, a patient should discuss any and all symptoms, even if they do not appear to be related. Clusters of unusual symptoms can themselves be a cardinal sign, as some conditions manifest in peculiar ways in the body. A care provider can also perform some basic testing to collect more information about the patient’s symptoms. Awareness of medical history can be important as well, because this might affect the reading of a cardinal sign.
When care providers identify a cardinal sign, they typically note it in the patient’s chart, to provide some information about what was observed. This can be helpful for someone reviewing the chart, as it may help that care provider understand how a diagnosis was arrived at, and what may have been considered before selecting a treatment plan. Incidental findings may also be noted for future reference. For example, a benign heart murmur is commonly recorded to make future care providers aware that it has been noted and evaluated.
Not all medical conditions present with a neat cardinal sign that can allow practitioners to identify and diagnose them quickly. Some symptoms are associated with multiple diseases and may require further investigation. Others can provide information about a process, but not the root cause. For example, bloody urine is an indicator of a problem in the kidney or bladder, but it doesn’t provide information about why the problem developed. The patient may need more diagnostic testing to get to the root cause, like a kidney stone or a bladder tumor.