116 PART THREE | DELIRIUM Table 3. Accuracy of the DOS. Accuracy of the DOS Wilson Score 95% CI lower limit Wilson Score 95% CI upper limit Sensitivity 1 0.958184 1.000004 Specificity 0.995997 0.955293 0.99966 PPV 0.946237 0.880258 0.976826 NPV 1 0.960748 1.000004 Abbreviations: CI, confidence interval; DOS, DeliriumObservational Scale; NPV, negative predictive value; PPV, positive predictive value The median DOS score of the DOS positive patients was 4.0 (IQR 4.0-6.0). Higher DOS scores correlated with higher DRS-R-98 total scores, see Table 4. Table 4. DRS-R-98 scores in DOS positive patients. DOS score N = DRS-R-98 total score median DRS-R-98 total score IQR 3-4a 50 22.3 19.0-24.1 >4-6b 23 23.5 21.5-26.0 >6c 20 26.0 21.8-27.4 Abbreviations: CI, confidence interval; DOS, Delirium Observational Scale; DRS-R-98, Delirium Rating Scale Revised 98 Distribution of the DRS-R-98 scores in patients screened positive for delirium with the DOS. When comparing the absolute DOS score to the DRS-R-98 total score a linear association was found; B = 0.677, 95% CI .229-1.126, p = .004. a1st and 2nd quartile; b3rd quartile; c4th quartile. Four of the five patients with a DOS of 3 or higher who were not confirmed to be delirious by the DRS-R-98 score (score <17.75), had DRS-R-98 total scores >12 points. The latter cut-off has been used as a more inclusive cut-off for delirium in some studies [30, 31]. One patient scored being delirious on the DOS but only scored three points on the DRS-R-98. We speculate that he/she may have displayed only temporarily signs of delirium which had resolved by the time the DRS-R-98 was conducted. Discussion To our knowledge this is the first study to evaluate the accuracy of the DOS in a large group of patients with advanced cancer. Our data showed that the DOS is a very sensitive and specific instrument to screen for delirium in hospitalized patients with advanced cancer. It might also give an impression of the delirium severity. Compared to other screening instruments, such as the CAM [15], NEECHAM Confusion Scale [16], and the Nu-DESC [5], the DOS has shown better sensitivity and specificity. It has the benefits that it is quick to administer, and does not require training [12].
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