the aging of the population has come along with an increase in the incidence of cognitive impairment ( ci ) , a clinical syndrome that , in about one - third of the patients , precedes dementia . an early detection of ci could produce benefits at different levels , including early dementia diagnosis , access to treatments , and delay or even reversion of cognitive deterioration [ 35 ] . primary care ( pc ) presents optimal characteristics of accessibility and continuity of care , which are essential for early detection and management of ci . in this vein , the focus of the pc physicians should be the detection of ci , rather than dementia . a separation of mild cognitive impairment ( mci ) and dementia would not only be difficult or arbitrary in many instances but would also lead to missing opportunities for treatment and research . the detection of ci requires a proactive attitude and the use of cognitive tests . in pc , in addition , these tests should have been specifically validated in the pc setting , with an adequate control of the potential influence of age , education , and other social variables . albeit not simple , rather long , and very influenced by education , the mini - mental state ( mms )   is still the most used cognitive test . as additional limitations , the mms displayed modest diagnostic utility for detection of ci in pc [ 10 , 11 ] and was recently protected by copyright . the mini - cog is a very simple and brief cognitive test that comprises a three - item verbal memory task and a simplified evaluation of the clock drawing test ( cdt ) . according to their authors , indeed , in a population - based study , this test was as effective as a formal neuropsychological battery for detecting dementia . the mini - cog was also well accepted by the patients , displayed good correlation with the mms , and was recently recommended in some consensus guidelines and reviews [ 1720 ] . however , there are very few studies addressing the yield of the mini - cog for detection of ci ( i.e. , both mci and dementia ) , which displayed conflicting results [ 21 , 22 ] . the objective of the present study was to evaluate the diagnostic utility of the mini - cog for detection of ci in patients who presented with complaints or suspicion of cognitive deterioration in pc . we analyzed data from two phase iii studies of evaluation of diagnostic instruments   that were conducted in two different cities of spain ( i.e. , madrid and granada ) . the study of madrid was conducted in the hermanos sangro health center ( health district 1 , autonomous community of madrid , urban area ) , and the study of granada was conducted in the almanjyar / cartuja , the casera de montijo , and the salvador caballero health centers ( health district granada norte , autonomous community of andaluca , urban area ) . the methods of these studies were described in detail elsewhere [ 24 , 25 ] . in the two studies , patients and caregivers were informed of the procedures and purpose of the studies and gave their consent to participate . the recruitment of patients and the administration of the screening instruments were performed in pc , whereas the formal neuropsychological evaluation and the final diagnosis ( gold standard ) were performed in specialized care ( sc ) , which replicates the standards of clinical practice . all the subjects who presented with complaints or suspicious ( either by informant or by family physician ) regarding cognitive dysfunction or cognitive deterioration were invited to participate in the study . a validated spanish version of the mms was utilized , with the modification of ignoring the possibility of spelling world backwards . the cdt was scored from 0 to 7 ; in one of the sites ( granada ) , the requested time was  ten past eleven ,  whereas in the other site ( madrid ) the requested time was  twenty to four . otherwise , the instructions for the clock drawing test in the two sites were alike ( i.e. ,  please , draw a big round clock , put all the numbers on it , and display the hands on ( requested time )  ) . the score of the mini - cog was obtained post - hoc , for the purpose of the present investigation . one point was given for every recalled word from the mms delayed recall task , and two additional points were given if the clock fulfilled the following conditions : ( a ) all the numbers from 1 to 12 were included and there was no repeated number , ( b ) all the numbers were in the right order and direction , and ( c ) the hands unequivocally displayed the requested time . mild cognitive impairment ( mci ) was diagnosed on the basis of the following criteria : ( a ) an abnormal performance was documented in at least one neuropsychological test ; ( b ) that abnormal performance was deemed to be of clinical relevance ( i.e. , not due to low premorbid level , lack of motivation , etc . ) , and ( c ) dementia criteria were not fulfilled . the diagnosis of dementia was made according to the 4th edition , text revised , of the diagnostic and statistical manual of mental disorders ( dsm - iv - tr ) . the cognitive diagnosis was performed by two senior neurologists with expertise in cognitive and behavioural neurology ( cc , jo ) after medical visit , neurological exam , mental status exam , and formal neuropsychological evaluation , which included tests of memory , attention / executive functions , language , and visual - spatial abilities [ 24 , 25 ] . throughout the study , laboratory determinations and other ancillary tests ( e.g. , cranial computed tomography scan ) the results of the screening instruments were not utilized for the cognitive diagnosis in the original studies . however , for the present investigation , the cdt , which was a screening instrument in the study of granada but was included in the formal neuropsychological evaluation in the study of madrid , was analyzed as a screening instrument . the screening instruments were administered before the neuropsychological and neurological exams were conducted , in different settings ( pc versus sc ) and by different professionals . the neurologists , who performed the cognitive diagnosis , were blind to the results of the screening instruments with the exception of the cdt in the study of madrid , as mentioned in the previous paragraph . complete verification was conducted ; that is , all the recruited patients received the same neuropsychological and neurological assessment and all of them received a final cognitive diagnosis , independently of the results in the screening instruments . there were some differences between the two studies regarding age and period of inclusion . in the study of madrid , only 50 year old patients were recruited , and the period of inclusion ran from april 1 , 2000 to october 31 , 2002 ( i.e. , 31 months ) . there was no age limit in the study of granada and the period of inclusion of that study ran from february 1 , 2008 to january 31 , 2009 ( i.e. , 1 year ) . the study of granada was approved by the hospital virgen de las nieves ethics committee , and participants signed informed consent . in the study of madrid , only verbal consent was required from patients and caregivers / informants . 
 statistical analysis . bivariate comparisons between quantitative variables were performed using student 's t - test , whereas qualitative variables were compared using chi - square and fisher exact tests . a potential influence of site was specifically addressed by means of two - factor ( site [ granada versus madrid ]  cognitive diagnosis [ ci versus no ci ] ) analysis of covariance ( ancova ) adjusted for age ( years ) , sex ( man versus woman ) , and education ( no or incomplete primary education versus primary or higher education ) .    the diagnostic utility of the mini - cog , the cdt , the mms , and the sum of the mms and the cdt scores ( mms + cdt ) was evaluated and compared for detection of ci ( mci or dementia ) using receiver operating characteristic ( roc ) curves . differences between the areas under the curve ( auc ) were analyzed using the hanley and mcneil correction to compare diagnostic tests in the same sample . in addition , the sensitivity ( sn ) , the specificity ( sp ) , the positive likelihood ratio ( lr+ ) , the diagnostic accuracy ( da ) ( proportion of patients correctly classified ) , and the kappa index of diagnostic concordance were obtained for all the cut points in all the tests . the best cut point was chosen for each test on the basis of maximization of da and kappa index . the interrater reliability of the mini - cog was evaluated in a subsample of 50 subjects ( first 25 subjects included in each site ) . four evaluators that were blind to one another and to all other study variables scored the clocks and the three - item recall tasks of those subjects , and the intra - class correlation coefficient ( icc ) was calculated . all the statistical tests were two tailed , and a level of p < 0.05 was chosen for statistical significance . the demographic and clinical characteristics of the total sample and of the two original samples are presented in table 1 . overall , there was predominance of female sex ( 72.0% ) , and the educational achievement was low ( 50.8% of the participants had not complete primary education ) . the frequency of illiteracy was particularly high in the participants from granada ( 14.1% versus 4.8% , p  0.009 ) . patients from granada also presented with a higher frequency of dementia ( 34.5% versus 9.1 , p  0.001 ) and obtained lower scores in all the cognitive tests ( table 1 ) .   as it was expected , the subjects with mci or dementia were older than the subjects with normal cognition ( nc ) . the subjects with ci had also less educational achievement and scored lower in all the cognitive tests ( table 2 ) . figure 1 represents the distribution of the mini - cog score in the two study groups . the score of the mini - cog was significantly influenced by age ( p  0.001 ) and education ( p  0.002 ) but not by sex ( p = 0.99 ) or study site ( p = 0.18 ) . a total of 16 participants belonging to the sample of granada ( 11.3% of patients from granada , 5.2% of the total sample , and 11 of them illiterates ) did not even try to draw the clock , in which case a zero score was given . the diagnostic yield of the mini - cog was inferior ( auc  se 0.78  0.02 ) , compared to that of the mms ( 0.84  0.02 , p  0.001 ) , the cdt ( 0.84  0.02 , p  0.001 ) , and the mms + cdt ( 0.86  0.02 , p  0.001 ) ( figure 2 ) . the best cut point of the mini - cog was 1/2 , with sn 0.60 ( confidence interval ( ci ) 95% 0.530.67 ) , sp 0.90 ( ci 95% 0.840.95 ) , lr+ 6.1 ( ci 95% 3.60.3 ) , da 0.73 , and kappa index 0.48  0.05 ) . the usually recommended cut point of the mini - cog of 2/3 displayed an inferior utility , with sn 0.78 ( ci 95% 0.710.84 ) , sp 0.59 ( ci 95% 0.510.68 ) , da 0.70 , and kappa index 0.38  0.04 ( table 3 ) . using a cut point of 22/23 , the mms had similar sn ( 0.76 , ci 95% 0.680.82 ) , but better sp ( 0.76 , ci 95% 0.680.83 ) and da ( 0.76 ) . as for the cdt , a cut point of 5/6 achieved similar results to those of the mms , with sn 0.76 ( ci 95% 0.680.82 ) , sp 0.78 ( ci 95% 0.700.85 ) , and da of 0.76 . the mms + cdt was slightly , but not significantly , superior to the mms or the cdt alone ( table 4 , figure 2 ) . the mini - cog displayed an excellent interrater reliability , with an icc ( sd ) of 0.97  0.01 . we pooled data of two homogeneous studies to ascertain the value of the mini - cog for detection of ci ( either mci or dementia ) in pc . the score of the mini - cog was obtained post - hoc , utilizing data from the mms and the cdt . the diagnostic utility obtained by the mini - cog was low , with an auc ( se ) of 0.78  0.02 and a percentage of correctly classified subjects of 70% , when the recommended cutoff of 2/3 was applied . a cut point of 1/2 obtained a slightly better yield ( 73% of cases correctly classified ) on the basis of a good specificity ( 0.90 ( ci 95% 0.840.95 ) ) but a low sensitivity ( 0.60 ( 0.530.67 ) ) , which was unacceptable for a detection test . the diagnostic utility of the mini - cog was inferior to that of the mms , which was moderate ( auc 0.84  0.02 ) . when the best mms cut point was applied ( i.e. , 22/23 ) , the sensitivity and specificity were modest ( 0.76 ( 0.680.82 ) ) , and the percentage of cases correctly classified did not reach 80% ( da 0.76 ) ( table 4 ) . these modest results of the mms coincide with other study conducted in pc   and with the results from two systematic reviews [ 11 , 18 ] . albeit also modest , the results obtained by the cdt in the present investigation were superior to the results obtained in previous studies   that led to disregard of the cdt for detection of mci . a possible explanation for our better results with the cdt is that this test was included , in one of the study sites , in the reference diagnosis . we also evaluated the diagnostic utility of the sum of scores of the mms and the cdt , but there was no significant gain , with a clear increase in testing time , when compared to the mms or the cdt alone . that result is also in agreement with a previous investigation .   in previous research , the mini - cog displayed good performance for detection of dementia , with figures that were similar   or even superior   to those obtained by the mms or the cdt . to the authors ' knowledge , only two studies had so far addressed the utility of the mini - cog for detection of ci , with conflicting results . in a sample of predominantly male old people , the results of the mini - cog were not satisfactory ( auc 0.64 ) , whereas , in a study conducted in a sample of predominantly  unserved ethnic minorities ,  a diagnostic accuracy of 0.83 was reported . the proportion of patients with dementia , that differed dramatically in those studies ( 3.3% dementia , 39.2% mci in holsinger 's study   versus 41.5% dementia , 21.3% mci in borson 's study ) , could explain the reported differences in the diagnostic yield of the mini - cog . our results , in a sample of intermediate characteristics ( 20.8% dementia , 36.5% mci ) ( table 1 ) , were also intermediate in terms of mini - cog diagnostic utility ( diagnostic accuracy 0.73 , auc 0.78 ) ( table 3 and figure 2 ) . clearly , all these data advise against the use of the mini - cog for detection of ci in settings where the suspected proportion of unrecognized dementia is low . we found a significant influence of education in the mini - cog performance , which was not in agreement with the original validation study . this discrepancy can be explained in the light of the low educational achievement of our sample ( table 1 ) . in the original validation study , all the participants had completed at least six years of education , whereas in the present study , a proportion of 50.8% of the subjects had not complete primary school , which in spain usually means less than eight years of formal education , and there was 9.1% of illiteracy ( table 1 ) . there is strong evidence of the influence of education and literacy on cdt performance [ 31 , 35 ] , and reasonably this should be the same with the mini - cog . in fact , poor yield of the mini - cog was previously reported for dementia detection in a sample of low educational level . overall , these data suggest a negative influence of education on the mini - cog , restricted to the most inferior educational strata .   our study had some limitations . first , the cdt was part of the reference diagnosis in one of the study sites , a limitation that could have overvalued the utility of the mini - cog and therefore would not essentially alter the study conclusions . second , the score of the mini - cog was obtained post - hoc from two different tests . this methodology was used by several researchers with exploratory purposes , including the original descriptions of the mini - cog [ 13 , 14 ] to ascertain the validity of the test . however , the results obtained by the mini - cog in each of the individual studies were similar ( data not shown ) , which strengthens the consistence and the external validity of the presented global results . as additional strength , the two pooled studies fulfilled the standards of high - quality phase iii diagnostic studies , a consecutive and systematic recruitment was conducted , and there were virtually no exclusion criteria . simplicity and shortness in time are indeed characteristics of the mini - cog , which are necessary for use in pc . however , the mini - cog was not a valid choice in the studied sample , and this result , which was consistent with previous research , advise against the use of the mini - cog , particularly in settings where the proportion of unrecognized dementia is low . in these settings , the use of tests that offer a wider range of tasks and score , yet maintaining acceptability and feasibility , seems more adequate . in light of the relevance of the detection of ci ,
objectives . to study the utility of the mini - cog test for detection of patients with cognitive impairment ( ci ) in primary care ( pc ) . methods . 
 we pooled data from two phase iii studies conducted in spain . 
 patients with complaints or suspicion of ci were consecutively recruited by pc physicians . 
 the cognitive diagnosis was performed by an expert neurologist , after formal neuropsychological evaluation . 
 the mini - cog score was calculated post hoc , and its diagnostic utility was evaluated and compared with the utility of the mini - mental state ( mms ) , the clock drawing test ( cdt ) , and the sum of the mms and the cdt ( mms + cdt ) using the area under the receiver operating characteristic curve ( auc ) . 
 the best cut points were obtained on the basis of diagnostic accuracy ( da ) and kappa index . 
 results . a total sample of 307 subjects ( 176 ci ) was analyzed . 
 the mini - cog displayed an auc ( se ) of 0.78  0.02 , which was significantly inferior to the auc of the cdt ( 0.84  0.02 ) , the mms ( 0.84  0.02 ) , and the mms + cdt ( 0.86  0.02 ) . 
 the best cut point of the mini - cog was 1/2 ( sensitivity 0.60 , specificity 0.90 , da 0.73 , and kappa index 0.48  0.05 ) . 
 conclusions . 
 the utility of the mini - cog for detection of ci in pc was very modest , clearly inferior to the mms or the cdt . 
 these results do not permit recommendation of the mini - cog in pc .