Mohammed T. Abou-Saleh

NON-COMPUTERIZED ASSESSMENT PROCEDURES 143post mortem retrospective staging procedures have been successfulin establishing remarkably robust clinicopathologiccorrelations in longitudinally-studied AD cohorts 6,7 .GLOBAL STAGINGEfforts to stage progressive dementia globally can be traced backat least to the early nineteenth century, when the Englishpsychiatrist, James Prichard, described four stages in theprogression of dementia: ‘‘(1) impairment of recent memory, (2)loss of reason, (3) incomprehension, (4) loss of instinctiveaction’’ 8 . More recently, the American Psychiatric Association’s1980 Diagnostic and Statistical Manual of Mental Disorders, 3rdedn (DSM-III) 9 recognized three broad stages in its definition ofprimary degenerative dementia. Subsequently, in 1982, two moredetailed global descriptions of the progression of dementia werepublished. One of these, the Clinical Dementia Rating (CDR)scale 10 described five broad stages from normality to severedementia. The other, the Global Deterioration Scale (GDS) 11 ,identified seven clinically recognizable stages, from normality tomost severe dementia of the Alzheimer type. These two globalstaging instruments, the GDS and the CDR, are generallycompatible except that the GDS is more detailed and specificand identifies two stages that the original CDR staging does not.One of these is a stage in which subjective complaints of cognitivedeficit occur (GDS stage 2). These subjective complaints are nowrecognized as occurring very commonly in aged persons 12–14 andconsensus workgroups have called attention to the importance ofthese symptoms and the need for more detailed study of theirnature and treatment 15–17 . Although this stage of subjectivecomplaints continues to be identified only by the GDS stagingsystem, recent studies have indicated that persons with thesecomplaints are at increased risk for subsequent overt dementia18,19 . Also, at the other end of the pathologic spectrum, theCDR did not identify any stage beyond that in which dementiapatients ‘‘require much help with personal care’’ and are ‘‘oftenincontinent’’, whereas the GDS identifies a final seventh GDSstage in which patients are already incontinent and over thecourse of which language and motor capacities are progressivelylost. Subsequently, two further stages were suggested for theCDR, corresponding to the GDS stage 7 range 20–22 .Staging procedures have been shown to be valid and reliablemethods for assessing the magnitude of pathology in AD andrelated dementing conditions. This validity and reliability isillustrated in this brief review for the GDS, probably the mostdetailed and explicit staging procedure.The validity of the GDS has been demonstrated in several ways.Cross-sectional studies have confirmed the consistency of theordinal sequence and the optimal weighting of the hierarchicallysequenced items embodied in the GDS stages in aging andprogressive Alzheimer’s disease (AD) 22–24 . Thus, the specificimpairments characteristic of each stage almost always followthe impairments described for the previous stage. Also, thegrouping of impairment characteristics within stages appears to beoptimal.For example, naturalistic study has supported the identificationof staging phenomena, largely identical to the GDS stages, byindependent lay-person observers. In this study 23 , a 30-itemquestionnaire derived from the GDS was completed by a relativeor caregiver for each of 115 patients with varying degrees ofdementia. Principal components analysis was used to combine theitems into a single composite scale which more reliably representsdistances between the 30 clinical manifestations along thecontinuum of cognitive decline. The study found that ‘‘the scalescores for the clinical manifestations were observed to cluster intorelatively discrete groups, suggesting naturally occurring stages orphases. Objective cluster analysis methods further confirmed thepresence of distinct transitions along the cognitive declinecontinuum’’. It concluded that the ‘‘utility of empirically derivedscale values in staging the course of primary degenerativedementia is suggested’’.The relationship between the GDS stages and mental statusassessments, other dementia assessments, scores on cognitive testsand other objective tests and in vivo assessments of brain changein aging and progressive dementia have been studied in considerabledetail 11,24 . These studies have indicated significantcorrelations between all of these measures of dementia severityand the GDS stages. However, the strongest relationships havebeen observed between comprehensive dementia assessments,such as the Mini-Mental State Examination (MMSE) 25 , and theprogression of dementia on the GDS 24 . The GDS also correlateswell with evaluations of actual functioning and activities of dailyliving in AD 26 and with independent physical markers of ADprogression, such as changes in neurologic reflexes 27 . Thus, theconstruct validity of the GDS has been well substantiated.At least six separate studies have examined the reliability of theGDS 28–33 . Reliability coefficients have ranged from 0.82 to 0.97 inthese studies, using disparate procedures in diverse settings. Thesestudies have indicated that the GDS is at least as reliable as anyother instrument upon which clinicians rely, such as the MMSE.In a reliability study in a nursing home setting 32 , the GDS wasfound to be somewhat more reliable than the MMSE. Importantly,GDS staging has also been shown to be a reliableprocedure when assessed using a telephone format 33 .Global staging scales such as the GDS have certain importantadvantages in dementia assessment. First and foremost, thesescales are strongly anchored to the clinical symptoms, behaviourand functional changes in progressive degenerative dementia andparticularly that of Alzheimer’s disease. Consequently, theydiscourage misdiagnosis. Unlike many mental status and otherdementia test instruments, global stages are relatively stable overtime and relatively resistant to practice effects. Equally importantly,global staging instruments are minimally influenced byeducational background and socioeconomic status, whereasmental status and similar assessments are strongly influenced bysuch factors. Also, global staging, and in particular the GDS,covers the entire range of pathology in central nervous system(CNS) aging and progressive dementia, whereas, for example,mental status assessments and most psychometric tests entirelyfail to distinguish GDS stages 1 and 2. Occasionally, patients maydisplay GDS stage 3 symptomatology and still score a perfect 30on the MMSE. Uncommonly, dementia patients may displayGDS stage 4 symptomatology, and still score a perfect 30 on theMMSE. Much more commonly, patients may display the clearcutdementia symptomatology characteristic of GDS stage 4 andachieve MMSE scores which are near-perfect or within the socalled‘‘normal’’ range. At the other end of the pathologicspectrum, most patients at GDS stage 6 achieve only bottomscores on traditional psychometric tests. Over the entire course ofthe GDS 7 stage, nearly all patients attain only zero scores on theMMSE. The GDS, however, describes a final seventh stage, overthe course of which patients may survive for many years.AXIAL AND MULTI-AXIAL STAGINGThe observation that the progression of dementia pathology isaccompanied by progressive changes in more specifically definedprocesses has resulted in efforts to stage dementia in terms ofthose processes. Generally, axial staging has attempted to exploitprogressive changes in cognition or functioning, althoughattempts have also been made to stage hierarchically progressivemood and behavioural changes, progressive motoric changes and