GÉNERO Y LA CONSTRUCCIÓN DE LA IDENTIDAD DE LA FEMINIDAD.

It is noted in Chapter 2 that many scoring systems have been proposed in the literature. Four of these systems are reported to produce good sensitivity, specificity, and diagnostic accuracy (Aprahamian et al., 2009; Pinto and Peters, 2009). These systems are proposed by (i) Shulman et al. (1986), (ii) Sunderland et al. (1989), (iii) Mendez et al. (1992), and (iv) Tuokko et al. (1992). Each system will be referred to in the rest of this thesis by the primary author’s name.

A comparative study is conducted using a sample of the CDT data. The sample consisted of cases which are deemed not to be severe, cases of very mild dementia, and MCI cases. The diagnosis of the latter two types is very challenging. These are considered to be the early stages of cognitive disorder, and so although it is difficult to diagnose disorder in these stages, it is critical that the symptoms are detected early.

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To test the effectiveness of each system in diagnosing positive dementia cases, a comparative study is conducted and the four aforementioned scoring systems are used to analyse 61 clock drawings to provide diagnoses. The sample contained CDTs from patients with four different diagnoses (AD, VaD, MCI and Normal). The ages of participants ranged from 35 to 93 years old. 35 of the drawings are produced by males and 26 by females. Figure 4.1 shows the distribution of the final diagnoses of these samples.

Figure ‎4-1: Distribution of diagnoses from the drawings used in the comparative study.

The selection of the positive cases is based on the score of the MMSE; the score is between 15 and 29. The scores relating to some of these drawings are well within the normal range, producing an average score of 22.5. For this reason, the majority of the drawings used in this comparative study presented a challenge, since many of them displayed only subtle errors.

19 19 7 16 0 2 4 6 8 10 12 14 16 18 20

AD VaD MCI Normal

N u m b e r o f d rawi n gs

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Results

4.1.1

Table 4.1 presents the results of this study, showing that the Tuokko scoring system produce the most reliable performance. The accuracy of this system (percentage of drawings diagnosed correctly) is 65.57 %, while the sensitivity (ability of the system to diagnose the positive cases) is 57.78 %, and finally the specificity (the accuracy of distinguishing the negative cases) is 87.50 %.

The other scoring systems produce a poorer performance as shown in Table 4.1. The accuracy of the other systems is between 36.07 % and 44.26 %, while the sensitivity is between 13.33 % and 26.67 %, and the specificity is between 93.75 % and 100 %.

Table ‎4-1: Results of the comparative study.

Shulman Sunderland Mendez Tuokko Correctly Identified 42.62 % 36.07 % 44.26 % 65.57 %

Sensitivity 24.44 % 13.33 % 26.67 % 57.78 % Specificity 93.75 % 100.00 % 93.75 % 87.50 %

Table 4.2 presents the percentage of correct diagnoses for each of the four scoring systems, within each of the cognitive impairment categories. While all the systems are able to recognise the majority of the ‘normal’ cases, Sunderland’s system is the only one to achieve 100 % accuracy in distinguishing these cases. For the abnormal cases with dementia, the table shows that all the scoring systems achieve their best diagnostic accuracy when diagnosing AD. However, this accuracy is still below 50 %, except for Tuokko’s system which predicts the AD cases with an accuracy of 63.16 %.

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The results also show that all the scoring systems produce low accuracy in diagnosing VaD and MCI cases. Two systems did not diagnose any of the patients suffering from the MCI disease.

Table ‎4-2: Performance of the scoring systems in correctly diagnosing each cognitive impairment.

Diagnosis Shulman Sunderland Mendez Tuokko AD 42.11 % 26.32 % 36.84 % 63.16 % VaD 10.53 % 5.26 % 26.32 % 31.58 % MCI 14.29 % 0.00 % 0.00 % 42.86 % Normal 93.75 % 100.00 % 93.75 % 87.50 %

Discussion

4.1.2

The aim of this study is to test the robustness of the scoring systems that are reported as being reliable in the literature. The study shows that Tuokko’s system is superior to the other systems in identifying the positive dementia cases because it produces the best sensitivity and the best trade-off between sensitivity and specificity. The study also shows that Sunderland’s system produces the worst accuracy in identifying the positive dementia cases. However, none of the four scoring systems produced high diagnostic accuracy.

These results are far inferior to the results reported by the developers of these scoring systems. In the literature, Shulman’s system is reported to produce a sensitivity of 86 %, and specificity of 7D %. The sensitivity Sunderland’s system is reported as 76 % and the specificity as 81 %, while Mendez’ system sensitivity is reported as 7D % and the specificity as 77 %. Toukko’s system is reported to produce the highest diagnostic accuracy among the four techniques, with a sensitivity of 92 % and a specificity of 86 %. The reason for the difference between

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the published results and the results of this study can be attributed to the data sample used. As noted earlier, most of the chosen samples are CDT drawings produced by MCI and mild dementia patients. The early diagnosis of these cognitive impairment stages is very important, as it allows medical interventions to slow the progress of the disease and treat the causes. However, it is very challenging to perform a diagnosis in these circumstances based on CDT alone.

The results of this study agree with the results of the comparative studies presented elsewhere, which concluded that the available CDT systems are not capable of diagnosing MCI and early stage dementia in the majority of cases.

In conclusion, the results obtained from the study show that changing the cut-off point of the scoring systems may improve the performance in diagnosing the cases of MCI and early stage dementia. Moreover, extracting new detailed CDT features may increase the robustness of the test in diagnosing the challenging cases. This is because the new features could reveal more information about clock drawing errors which are specific to the early stages of dementia.

Clock Image Enhancement