An elderly patient is brought by family for confusion. You wonder whether this is delirium, or whether dementia may have developed. As covered in a previous post, dementia is defined by a deficit in memory as well as one other cognitive function. You can easily test for 3 item recall and clock drawing. But for those tests to be valid at all you have to exclude delirium. The hallmark of delirium is inattention.
Have them count the months backward, starting with December, to see if they can maintain attention. This is 83% sensitive and 90% specific for delirium.(O’Regan JNNP 2014) Interestingly, the addition of confirmatory tests (CAM) to improve specificity worsened sensitivity to 62%. Of course, delirium is not a binary event but exists across a spectrum. So some of the deviation from perfection could merely indicate a different location on the spectrum of illness severity. In light of its simplicity and ease of use, I recommend using months backward in your ED delirium screening. This is not a gold standard but does contribute value in raising or lowering the probability.
You assess months backward and the patient goes no further than November. You suspect delirium, and are relieved when you discover a UTI. You give the family assurance that the confusion will improve, though she will need to see the family physician in follow-up to confirm cognitive function.
Take Home Points
-Delirum, in the ED, is identified by inattention
-Have the patient count the months backward as a fast bedside screening test