SQiD vs CAM Redux

This was a blog post I wrote back in 2011 on another blog, The Practical C-L Psychiatrist. SQiD is short for Single Question in Delirium and it’s a very short and effective screen for delirium, if you have a reliable informant. I also mention the Edinburgh Delirium Test Box (EDTB). It has been further developed into a smartphone app.

“The November Vol. 3 issue of the Annals of Delirium published a summary of an interesting study of a Single Question in delirium (SQiD) as a screen for delirium compared to the Confusion Assessment Method (CAM), the Memorial Delirium Assessment Scale (MDAS) and a psychiatrist interview[1].

The question “Do you think (name of patient) has been more confused lately?” was put to a friend or relative of 21 patients. Compared with psychiatric interview, the SQiD achieved a sensitivity and specificity of 80% (95% CI 28.3-99.49%) and 71% (41.90-91.61%) respectively. The CAM demonstrated a negative predictive value (NPV) of 80% (51.91-95.67%) and the SQiD showed an NPV of 91% (58.72-99.77%). The CAM in the study had only a 40% sensitivity used by minimally trained clinical users.

The negative predictive value of a test tells you how likely it is that you actually don’t have the condition or disease. It’s defined as the number of true negatives (people who test negative who are not affected) divided by the total number of patients who test negative and it varies with test sensitivity, test specificity, and disorder prevalence. The sensitivity of a test is how accurately it detects patients who are positive for the disorder (in this case delirium). If 100 patients are positive for the disorder, then a test that is 80% sensitive will detect 80 of those cases and miss 20 actual cases of the disorder. Specificity is defined as how accurately a test detects patients who do not have the disorder. In our delirium example, if 100 patients are free of the disorder, then a test that is 71% specific will correctly tell 71 of those people that they are not affected and will incorrectly tell 29 that they have the disorder when they don’t.

This seems to suggest that a single question screening question packs a fair punch compared to screening instruments and psychiatric interview for identifying delirium. The CAM takes a few minutes to complete and requires training to achieve optimal identification rates.

The authors suggest the SQiD deserves further study and their results seem to support the conclusion. The study is limited by small sample size, but intuitively the premise is appealing. This is one of the quickest tests for delirium applicable and can be applied by almost anyone.

Single question screening exams for depression are not unheard of so there is precedence for the SQiD. You just have to be careful about what you say in front of patients and families. “Go ahead and run the squid on Mr. Jones” could raise a few eyebrows.

This is possibly a low tech solution in a pinch when the CAM forms file is empty or the battery is low on the Edinburgh Delirium Test Box (EDTB)[2]. The EDTB is a more high-tech solution to testing for what neuropsychologists believe what one of the main abnormalities is in delirium—lack of sustained attention. It’s a computerized neuropsychological testing device.

And that face-off would be called SQiD versus Box.”

References:

1.         Sands, M., et al., Single Question in Delirium (SQiD): testing its efficacy against psychiatrist interview, the Confusion Assessment Method and the Memorial Delirium Assessment Scale. Palliative Medicine, 2010. 24(6): p. 561-565.

2.         Brown, L.J.E., et al., Detecting deficits of sustained visual attention in delirium. Journal of Neurology, Neurosurgery & Psychiatry.

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