117 6 DELIRIUM | PART THREE Strengths of the study are that we were able to include a large group of patients, and that the DRS-R-98 assessment was performed by an independent assessor who was blinded to the DOS score of the patient. Also, the nursing staff was already used to complete the DOS scale during routine care, so we did not need a run-in or training period for the study. In addition, during the conduct of the study the nurses gave very positive spontaneous feedback on the effort it took to complete this questionnaire. There are several limitations to this study. First, the observed incidence of delirium at the study siteswas low [8]. Therefore, it was necessary to adjust the results for non-verification. Even after this adjustment, wehave convincing results that theDOS is an accurate screening instrument for delirium screening in patients with advanced cancer. Second, while other baseline characteristics were evenly distributed over the DOS positive and DOS negative patients, patients who were DOS negative were younger than the DOS positive patients. This is concordant with the fact that advanced age is one of the known risk factors for the development of delirium [2]. Using age-matched comparators would however hamper the applicability of this study to the whole population of hospitalized patients with advanced cancer. For this study we used a DRS-R-98 score of >17.75 as a cut-off for delirium. The patients who screened positive for delirium with the DOS scale but not with the DRS-R-98, had (except for one) DRS-R-98 scores >12, which has been classified as subsyndromal delirium in previous studies [30, 31]. One might argue that it might be beneficial for these patients as well to be treated for their symptoms. Conclusions The DOS is an accurate instrument for detection of delirium in a population of hospitalized patients with advanced cancer. The DOS can be completed by nurses based on the observations made during regular nursing care, which makes it easily applicable as a screening tool for delirium in patients with advanced cancer. By early recognition and adequate treatment of this distressing delirium syndrome the quality of life of patients with advanced cancer can be improved. Acknowledgments This work was supported by ZonMw The Netherlands Organization for Health Research and Development (grant number 1151.0011). The funding source did not have a role in the design, analysis and interpretation of data; in the writing of the report; nor in the decision to submit the article for publication.
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