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Can IQCODE differentiate Alzheimer's disease and frontotemporal dementia?

Research Letter Can IQCODE differentiate Alzheimer's disease and frontotemporal dementia? SIR—The differential diagnosis of Alzheimer's disease (AD) and behavioural variant frontotemporal dementia (bvFTD) may be difficult because the clinical features and diagnostic criteria for these conditions show a degree of overlap [1]. A number of bedside test instruments, examining cognitive, be-havioural and/or functional domains, and based on patient or informant report, have been suggested to be helpful in making the distinction between AD and bvFTD [2], but those examined in this clinic have not proved particularly useful, namely the Addenbrooke's Cognitive Examination VLOM ratio [3], the Instrumental Activities of Daily Living Scale [4] and the Cambridge Behavioural Inventory [5]. The Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE) is a widely used screening test for dementia, providing information complementary to cogni-tive tests [6]. A lower score (range 1–5) represents better performance. As part of ongoing studies of IQCODE in this clinic based in secondary care [7], the utility of IQCODE scores to differentiate AD and bvFTD was examined. All cases with diagnoses of either probable AD (using NINCDS-ADRDA criteria [8]) or bvFTD (using Neary criteria [9]) and with IQCODE (long form [10]) performed at the same time as initial clinical and neuropsychological assessments were identified from clinic records over an 18-month period (July 2007–December 2008 inclusive), and IQCODE scores for patients with AD and bvFTD were compared. Results As expected, the bvFTD cases (n = 13) had a younger age at diagnosis (range 47–76 years, mean 60.2 +/− 7.3 years) than the AD cases (n = 41; age range 52–92 years, mean 70.6 +/− 9.0 years) and a greater male preponderance (bvFTD M:F = 11:2; AD M:F = 15:26). Mean IQCODE score for bvFTD patients was 4.34 +/− 0.31 and for AD patients was 3.94 +/− 0.39, a difference which proved statistically significant (t = 3.25, df = 52, P < 0.01). The null hypothesis that the proportion of patients with IQCODE score ≥ 4.0 did not differ significantly between the bvFTD (11/13 = 84.6%) and AD (17/ 41 = 41.4%) groups was examined. The result of the χ 2 test permitted rejection of the null hypothesis (χ 2 = 6.51, df = 1, P < 0.02), a finding corroborated by the Z test (Z = 2.67, P < 0.01). Mean scores for each of the 26 questions in the IQCODE long form [10] were compared between AD and …