C-reactive protein levels and delirium in a rehabilitation ward
SIR—In their research letter recently published in this journal [1], Macdonald found that high levels of C-Reactive Protein (CRP) independently predict the incidence of delirium, while low CRP levels predict the recovery from delirium at any time during hospitalisation.We want to contribute to this topic from our own personal data, with reference to our experiences in managing delirium in our rehabilitation and aged care unit (RACU). From 1 June 2005 to 31 December 2006, 110 patients underwent a diagnosis for delirium, on admission (prevalent) or during their hospital stay (incident). Source of admission were orthopedic or medical wards, while 29 patients came from home. The diagnosis for delirium was performed by experienced geriatricians (GB and SS), using the Confusion Assessment Method (CAM) [2]. All patients underwent a multidimensional assessment, including demographics, clinical (Charlson Index, APACHE II score [3]), nutritional (Body Mass Index and albumin serum levels), cognitive (Mini-Mental State Examination, Clinical Dementia Rating scale) and functional (Barthel Index on admission and Instrumental Activities of daily living) status. The CRP serum levels (quantitative determination; Konelab) were available for 98 cases of prevalent delirium and in 12 cases of incident delirium. Among individuals with prevalent delirium, 41 had surgical causes, 33 had infective causes (i.e. pneumonia or urinary tract infections) and 24 had a mix of non-infective causes (stool or urinary retention, dehydration, and iatrogenesis). Eight individuals with incident delirium had infective causes, while four had non-infective causes. Table 1 shows the characteristics of different patient groups.
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As expected, CRP serum levels changed coherently with the phases of delirium (onset and resolution) across groups. In fact, in patients with prevalent delirium, the CRP levels are elevated on admission and low at delirium resolution either in those with surgical, infective, or non-infective causes; in patients with incident delirium, the CRP levels are lowest on admission (when patients are not delirious), highest when delirium develops and, again, low at delirium resolution, both in the infective and non-infective groups. Although the CRP levels were higher on admission in patients developing incident delirium for infective causes in comparison to those with non-infective causes, the change from admission to delirium onset in CRP levels was similar for both groups.
However, it should be underlined that in patients with prevalent delirium for non-infective causes, the CRP serum levels were lower when compared to the levels of patients with infective and surgical causes, suggesting that physiopathological mechanisms precipitating delirium significantly influence the amount of inflammatory response.
We agree with Macdonald that the CRP serum levels may help to focus clinical attention on the diagnosis and the management of delirium. However, although CRP may be viewed as a measure of inflammatory activity, it may not be forgotten that it actually captures only one specific aspect of inflammation, which is not necessarily the most relevant for delirium [4].
1 Rehabilitation and Aged Care Unit, ‘Ancelle della Carità’ Hospital, Cremona, Italy
2 Geriatric Research Group, Brescia, Italy
3 University Tor Vergata, Rome, Italy
* To whom correspondence should be addressed E-mail: giuseppebellelli{at}libero.it; bellelli-giuseppe{at}ancelle.it
References
- Macdonald A, Adamis D, Martin F, et al. C-reactive protein levels predict the incidence of delirium and recovery from it. Age Ageing (2007) 36:222–5.
[Free Full Text] - Inouye SK, Van Dyck CH, Horwitz R, et al. Clarifying confusion: the confusion assessment method, a new method for detection of delirium. Ann Intern Med (1990) 113:941–8.
[Abstract/Free Full Text] - Knaus WA, Draper EA, Wagner DP, Zimmerman JE. APACHE-II: a severity of disease classification system. Crit Care Med (1985) 13:818–29.[Web of Science][Medline]
- Marcantonio ER, Rudolph JL, Inouye SK, et al. Serum Biomarkers for delirium. J Gerontol Med Sci (2006) 61A:1281–6.
[Abstract/Free Full Text]
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