Introduction: This study was undertaken to assess the value of Serum Clusterin (SC) in assessment of Cognitive Dysfunctions (CD) in COPD patients.
Material and methods: All COPD patients and age and sex matched healthy subjects were assessed in detail. They were then subjected to Hindi Mental State Examination (HMSE) in an attempt to assess CD in them. Their SC levels were also measured using quantitative sandwich enzyme immunoassay technique.
Results: A total of 75 COPD patients and 10 controls could be assessed during the intake period. Fifty four out the 75 COPD patients (72%) were detected to have CD on the basis of abnormal HMSE scores (< 25). On the other hand CD could be detected in 52 out the 75 COPD patients (69%) while using SC levels of > 110 µgm/ml as criteria for CD. There was an inverse but highly significant correlation between abnormal HMSE scores and SC levels (p < 0.0001). Age, sex, duration of illness, the type of smoking, pack years of smoking or Body Mass Index (BMI) poorly correlated to SC levels (p > 0.05) but the latter significantly correlated to decreasing PB FEV1, sPO2 < 90% (p < 0.001) and severity of COPD. History of exacerbations needing hospitalization contributed the most to CD in COPD patients.
Based on these findings it can be concluded that serum SC levels can be safely used to assess CD in COPD patients.
Chronic Obstructive Pulmonary Disease (COPD) is defined as a common preventable and treatable disease, characterized by persistent airflow limitation that is usually progressive and associated with an enhanced chronic inflammatory response in the airways and the lung to noxious particles or gases. Exacerbations and comorbidities contribute to the overall severity in individual patients [1]. Systemic inflammation also plays an important role in the severity and the downstream adverse clinical health effects of the disease [2-4].
Cognitive Dysfunctions (CD) in old age COPD patients were first recognised by Chyou et al., [5] but its nature and level were fully described by Borson et al., [6] and Dodd et al., at a later date [7]. Thakur et al., [8] used Mini Mental State Examination (MMSE) to assess CD in COPD patients. A Hindi version of MMSE to assess CD, namely the Hindi Mental State Examination (HMSE) was made available at a later date [9]. However, administrating HMSE is a time consuming affair and is often not feasible in a busy outpatient department. A biochemical parameter to assess CD, therefore, is the need of the hour.
Since Serum Clusterin (SC) was already in use to assess CD in several other diseases, it was reasoned that it could be used in COPD patients also. Li et al., [10] were the first to do so and they found that highest serum clusterin levels were found in severe COPD patients when compared to control subjects. Based on this they advocated the use of SC assays to assess of CD in COPD patients but no further studies are available to substantiate their findings. The present study was therefore undertaken at NIMS Medical College, Jaipur, Rajasthan (India) to know whether SC can be used as an alternative tool to the questionnaire based mental assessment of CD in COPD patients.
All the patients reporting at the outpatient department of Respiratory Medicine, NIMS hospital, Jaipur (India) from July 2013 to August 2014 with symptoms suggestive of COPD were recruited for the study. Approval of the Institutional Ethics Committee was obtained. A written informed consent was also taken from all the patients and controls for the study.
All these patients were initially evaluated with a detailed present and past clinical history, comprehensive physical examination and investigations that included total/differential blood counts, erythrocyte sedimentation rate, total eosinophil count, haemoglobin, random blood sugar, urea, creatinine, SGOT/PT, 2 sputa samples for acid fast bacilli by Zhiel Nelson staining, urine routine examination, X-ray chest posterio-anterior view and a 12 lead electrocardiogram. Spirometry was then performed in sitting position as per American Thoracic Society (ATS) guidelines to measure Forced Vital Capacity (FVC), Forced Expiratory Volume in first second (FEV1) and FEV1/FVC%, pre and post inhalation of salbutamol 200μg. ATS criteria [11] were used to diagnose COPD i.e., Post Bronchodilator Forced Expiratory Volume in 1st second (PB FEV1) of < 80% of predicted, FEV1/FVC < 70% and PB improvement in FEV1 of less than 12% or 200 ml.
All such diagnosed COPD patients in the age group of 40 to 90 were included in the study but patients with past history suggesting bronchial asthma, other chronic illnesses like malignancy, diabetes mellitus, coronary artery disease, stroke, renal or hepatic disease, injury to head, dementia, sleep disorders, obstructive sleep apnea or psychiatric disorders or exposure to pesticides or toxins were excluded. Ten age and sex matched healthy subjects were also included to serve as controls.
The level of dyspnoea in the study patients was assessed using modified British Medical Research Council (mMRC) questionnaire. The number of exacerbations and number of hospitalizations in the past 3 years, based on history and medical records of the patients, were also recorded. The patients were classed as I to IV on the basis of PB FEV1 (GOLD class of severity) and as category A to D on the basis of the combined risk assessment of individual patient [1]. Pulse oximetry was used to evaluate the Oxygenation status (sPO2) of the patients.
All the subjects were then subjected to HMSE, using 12 items and 23 questions to assess cognitive functions [9]. Venous blood samples were drawn from all of them at around 8.00 AM. The latter were then centrifuged for 20 min at 3,000 rpm and the supernatants were stored at -20°C but then brought to room temperature for measurement of SC, using quantitative sandwich enzyme immunoassay technique on a commercially available ELISA kit, as per the manufacturer’s instructions [12]. Readings were made directly at 450 nm with using Thermo Fisher Scientific Multi scan EX Micro plate Reader.
Since normal range of HMSE scores and SC levels are not available for universal use, the mean of HMSE scores minus twice the Standard Deviation (SD) in normal subjects was used as cut off for abnormal HMSE and the mean of SC levels plus twice the SD in the normal subjects was taken as cut off for abnormal SC levels.
The data so obtained were tabulated and assessed for statistical significance using student’s t, Anova, X2, Fisher Exact test as and where applicable. Cramer’s V correlation was used to detect correlation between SC levels and various patient variables. Values of p < 0.05 were considered as significant.
A total of 75 patients were COPD patients and 10 age and sex-matched controls, could be included in the study during the study period. Nineteen, 09, 16 and 31 patients were classed as category A, B, C & D, respectively. The basic parameters of these subjects are shown in table 1. There were no inter category differences with regard to age, sex or BMI (p > 0.1). Most patients were bidi smokers but there were no inter group differences with regard to smoking status, type of smoking or pack years of smoking (p > 0.3). The mean duration of illness (p = 0.014) and sPO2% < 90% were higher in category D as compared to the rest (p = 0.0001).
Parameter |
Category A COPD patients N = 19 |
Category B COPD patients N = 09 |
Category C COPD patients N = 16 |
Category D COPD patients N = 31 |
Normal subjects N = 10 |
P value |
Mean Age in years |
57.68 ± 11.73 |
53.88 ± 10.14 |
57.50 ± 6.27 |
62.06 ± 9.35 |
56.20 ± 6.76 |
0.1197 |
Sex -Male -Female
|
17
02 |
07
01 |
15
02 |
26
05 |
09
01 |
0.9497 |
Mean duration of illness in years |
2.94 ± 1.79 |
3.72 ± 0.52 |
4.43 ± 2.19 |
5.35 ± 3.26 |
- |
0.0139 |
Mean Body Mass Index in kg/M2 |
19.01 ± 3.62 |
19.20 ± 4.17 |
19.26 ± 2.86 |
18.54 ± 3.41 |
19.65 ± 3.89 |
0.8968 |
Smoking status -Current -Ex-smoker |
14
05 |
04
05 |
08
08 |
16
15 |
- |
0.3359 |
Type of smoking
-Bidi -Other types
|
17
02 |
08
01 |
14
02 |
25
06 |
- |
0.9027 |
Mean pack years of smoking |
41.53 ± 29.56 |
41.87 ± 11.36 |
42.10 ± 11.75 |
44.64 ± 13.87 |
- |
0.9517 |
sPO2 levels in % -<90 -> 90
|
00
19 |
00
09 |
01
15 |
14
17 |
- |
0.0001 |
Mean PB FEV1% |
63.78 ± 9.95 |
61.81 ± 6.10 |
38.81 ± 6.02 |
37.58 ± 11.85 |
- |
0.0001 |
Table 1: Basic parameters of the COPD patients and normal subjects.
sPO2 = Haemoglobin Saturation in %; PB FEV1% = Post bronchodilator forced expiratory volume in 1stsecond of expiration in %
The mean HMSE score in normal subjects was 30.30 ± 2.68. Therefore a cut off value for normal subjects was taken as 24.94 i.e., up to 25. Based on abnormal HMSE scores (< 25), fifty four out the 75 COPD patients (72%) were diagnosed to have CD, as is shown in table 2. Cognitive dysfunctions were more common in category D patients as compared to the rest (0.00001).
Cognitive impairment |
Category A COPD patients |
Category B COPD patients |
Category C COPD patients |
Category D COPD patients |
Total |
Yes ( HMSE < 25) |
05 |
07 |
12 |
30 |
54 |
No (HMSE ≥ 25) |
14 |
02 |
04 |
01 |
21 |
Total |
19 |
09 |
16 |
31 |
75 |
Table 2: Cognitive impairment in COPD patients based on HMSE score.
X2= 48.95; p < 0.00001
The mean SC level in normal subjects was 68.10 ± 21.64 µgm/ml. Therefore a cut off value for normal subjects was taken as 110.34. Table 3 shows the prevalence of CD in different risk groups of COPD patients. Fifty two out the 75 COPD patients (69%) were diagnosed to have CD. Higher number of category D patients suffered from CD as compared to the rest (< 0.00001).
Cognitive impairment |
Category A COPD patients |
Category B COPD patients |
Category C COPD patients |
Category D COPD patients |
Total |
No (SC < 110) |
17 |
00 |
06 |
00 |
23 |
Yes (SC >110) |
02 |
09 |
10 |
31 |
52 |
Total |
19 |
09 |
16 |
31 |
75 |
Table 3: Cognitive impairment in COPD patients based on SC levels in µgm/ml.
X2= 48.95; p < 0.00001
Table 4 shows the correlation of CD using HMSE score Vis a Visa SC levels. It shows that there was a highly significant correlation between the 2 methods, used for assessment of CD in COPD patients (< 0.0001).
Cognitive impairment using HMSE Score |
Cognitive impairment using SC level |
Total No. of patients |
Yes |
No |
Yes |
51 |
03 |
54 |
No |
01 |
20 |
21 |
Total |
52 |
23 |
75 |
Table 4: Correlation of cognitive impairment in COPD patients using HMSE Vis a visa SC levels.
X2= 57.20; p < 0.00001
The correlation between SC levels and various parameters of the study patients are shown in table 5. Serum clusterin poorly correlated to age, sex, duration of illness, the type of smoking, pack years of smoking or the BMI (p > 0.05) but there was a significant correlation between SC levels and PB FEV1 , different risk categories and sPO2 levels < 90% (p < 0.001).
Parameter |
Mean SC in µgm/ml |
P value |
Age in years |
≤ 50 51-60
> 60 |
118.01 ± 37.60 141.62 ± 53.54
143.15 ± 36.90 |
0.579 |
Sex |
M
F |
137.73 ± 41.05 126.63 ± 34.11 |
0.951 |
Total duration in years |
< 3 3-5
> 5 |
122.82 ± 36.72 141.37 ± 53.14
155.96 ± 29.66 |
0.0776 |
Pack years of smoking |
< 30 30-40
> 40 |
110.56 ± 35.73 143.40 ± 51.57
139.82 ± 41.00 |
0.1861 |
Body Mass Index |
< 18 18-22
> 22 |
141.52 ± 46.95 128.23 ± 41.56
131.21 ± 41.47 |
0.7521 |
sPO2% |
< 90
> 90 |
128.48 ± 45.78
167.25 ± 23.76 |
0.0009 |
PB FEV1% |
≥ 50 ≥ 30-< 50
< 30 |
110.65 ± 35.38 156.15 ± 44.86
156.78 ± 31.61 |
0.0010 |
Risk category |
A B C
D |
86.54 ± 17.22 128.43 ± 9.77 123.25 ± 27.73
175.62 ± 33.63 |
0.0001 |
Table 5: Correlation of SC levels with various parameters of the COPD patients.
sPO2 = Haemoglobin Saturation in %; PB FEV1% = Post bronchodilator forced expiratory volume in 1st second of expiration in %
Since mean SC levels were similar in category B (128.43 ± 9.77 µgm/ml) and category C patients (123.25 ± 27.73 µgm/ml) of this study, the individual parameters used in the combined risk assessment of COPD were also correlated to SC levels. There was a significant and direct correlation between SC levels and hospitalizations per year, exacerbations per year, mMRC and GOLD class (p < 0.0001) in that order, the respective correlation coefficient (rs) being 0.852, 0.811, 0.739 and 0.519.