ORIGINAL ARTICLE

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RISK FACTORS FOR DIABETIC RETINOPATHY IN DIABETICS SCREENED USING FUNDUS PHOTOGRAPHY AT A PRIMARY HEALTH CARE SETTING IN EAST MALAYSIA

PS Mallika¹ MS; PY Lee² MFamMed; WL Cheah³ PhD CommNutr; JS Wong⁴ MRCP; SAR Syed Alwi⁵ MFamMed; H Nor Hayati⁶ MFamMed; AK Tan^1,7 MD.
¹Department of Ophthalmology, Faculty of Medicine and Health Sciences, Universiti Malaysia Sarawak, Kuching, Sarawak, Malaysia. (Mallika Premsenthil, Tan Aik Kah)
²Department of Family Medicine, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, Malaysia. (Lee Ping Yein)
³Department of Community Medicine and Public Health, Faculty of Medicine and Health Sciences, Universiti Malaysia Sarawak, Malaysia. (Cheah Whye Lian)
⁴Department of Medicine, Sarawak General Hospital, Kuching, Sarawak, Malaysia. (Wong Jin Shyan)
⁵Department of Family Medicine, Faculty of Medicine and Health Sciences, Universiti Malaysia Sarawak, Malaysia. (Syed Alwi Syed Abdul Rahman)
⁶Heartscans International, 107&109 Jalan Maarof, Kuala Lumpur, Malaysia. (Nor Hayati Hassan)
⁷Department of Ophthalmology, Universiti Kebangsaan Malaysia. (Tan Aik Kah)

Address for correspondence: Assoc Prof Dr Lee Ping Yein, No. 43, Jalan Jalil Perkasa 10, Taman Esplanad, Bukit Jalil, 57000 Kuala Lumpur, Malaysia. Tel: +603 8994 0027, Fax: 03-8947 2328, Email: pylee02@hotmail.com

Funding and conflict of interest: None.

INTRODUCTION

Diabetes mellitus (DM) is a significant public health problem worldwide. The total number of people with diabetes is projected to increase from 171 million in 2000 to 366 million in 2030.¹ The prevalence of DM is expected to reach epidemic proportions with the main burden of disease in developing countries.² World Health Organisation (WHO) estimates a 3-fold rise of the disease in Asia.²

The prevalence of DM in Malaysia has increased from 0.6% in 1960 to 14.9% in 2006.³ Reasons for the increase in prevalence includes rapid urbanisation with reduced physical activities, changes in the dietary habits, longevity, reduction in the death rates and increase prevalence of obesity.

Diabetic retinopathy (DR) is a common complication of both type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM).⁴ The prevalence of DR increases with the duration of diabetes and the patient’s age. Other risk factors are: systemic arteriosclerosis, anaemia, renal impairment and pregnancy.^5-7 DR is the leading cause of blindness in the working-aged people.⁸ The prevalence of DR is likely to increase with the projected increase of T2DM in the developing countries,² adding to the already existing burden of preventable blindness diseases like cataract, corneal disease, refractive error and retinal diseases. The prevalence of all DR in Malaysia was 12.3% for T1DM and 22.3% for T2DM.⁹ Most published Malaysian data are primarily hospital based.^9-12 This study reports on the prevalence of DR and risk factors among diabetic patients, who underwent fundus photography screening in a primary care setting of Sarawak, East Malaysia. With the limited funding, this study aimed to explore the preliminary data to help in the planning of more effective screening and preventive strategies of DR at the primary health care setting. Sarawak has the largest land area of all the 13 states in Malaysia, situated in the Borneo Islands. The total population is about 2.07 million of which nearly 579,900 people live in the state capital, Kuching.¹³

MATERIALS AND METHODS

This study is a cross-sectional prospective study conducted on all diabetes patients who had undergone screening fundus photography in 2004, in Jalan Masjid Health Centre (KKJM). This clinic is the largest of the three public primary health care clinics in Kuching. Nearly 4500 diabetic patients were registered in the diabetes clinic in KKJM. Fundus photography for the assessment of DR was introduced at KKJM in the year 2004. All patients who were not previously diagnosed to have DR were included for the fundus photography screening at the primary care clinic. Patients who had cataracts for which fundus photography could not be done or those with fundus photographs that were unreadable were excluded. Our study was approved by the Malaysian IRB/IEC MOH Research & Ethics Committee (MREC) (NMRR-10-836-6973). Data was retrieved from the clinic based diabetes cards and the fundus photography assessment forms.

Information obtained included: socio demographic details, type of diabetes, duration of diabetes, compliance to treatment (based on patients’ self-report from health provider interview and regularity of follow-up) , presence or absence of systemic hypertension, proteinuria or microalbuminuria, coronary heart disease, awareness of DR, any prior review by an ophthalmologist, presence of visual complaints and smoking status. The following parameters were also included in the study: body mass index (BMI), blood pressure (BP), glycosylated haemoglobin (HbA_1c) and fasting lipid profile (total cholesterol, triglycerides, low density lipoprotein [LDL], high density lipoprotein [HDL]).

The diagnosis of DM was made according to the Malaysian Diabetes Practice guidelines.¹⁴ The target for control of DM and hypertension were based on the recommendations by the International Diabetic Federation (IDF),¹⁵ where HbA_1c of <6.5% is optimal, 6.5 to 7.5% is fair and >7.5% is sub-optimal. The BP target for control was categorised into optimal <130/80 mmHg, fair 130/80 to 140/70 mmHg and sub-optimal >140/90 mmHg. The target for lipid profile was total cholesterol ≤4.5 mmol, triglyceride ≤1.7 mmol/L, LDL-C ≤2.6 mmol and HDL-C ≥1.1 mmol/L.¹⁶ The classification of obesity was based on Malaysian guidelines where BMI of <18.5 kg/m² is underweight, 23.0-27.4 kg/m² is overweight and ≥27.5 kg/m² is obese.¹⁷ Smokers were defined as those who have a history of cigarette smoking in the past one month.

Eye examination consists of visual acuity testing by Snellen chart followed by fundus photography for DR assessment. Fundus photography was performed by a trained medical assistant using Topcon TRC-50VT camera (Topcon Corporation, Tokyo, Japan). Each eye was subjected to two non-stereoscopic 45º photographs; macula-centred and optic disc centred photograph. The photographic fields were equivalent to Diabetic Retinopathy Study (DRS) standard fields 1 and 2. The fundus pictures were reviewed by a family physician and an ophthalmologist. When there was disagreement, the ophthalmologist made the final decision. The eye with the more severe DR was taken into analysis. Visual loss was classified as mild (6/9 to 6/12), moderate (6/18 to 6/60) and severe (worse than 6/60). Fundus photographs were graded as having no DR, NPDR, PDR and maculopathy.

The international clinical DR severity scale adopted by the American Academy of Ophthalmology (AAO)^18,19 were used to classify patients into non-proliferative diabetic retinopathy (NPDR), proliferative diabetic retinopathy (PDR) and maculopathy. NPDR was defined as present of any or more of the following: micro-aneurysms, intraretinal hemorrhage, venous beading, or intraretinal microvascular abnormalities (IRMAs) AND no signs of proliferative retinopathy. PDR was defined as neovascularization or vitreous or preretinal haemorrhage. Diabetic macular oedema (DME) was present when any retinal thickening or hard exudates were present in the posterior pole.

Data entry, cleaning and analysis was done using SPSS version 17.0 for windows. Socio-demographic characteristics of the study sample were analysed and presented using appropriate descriptive statistics. The Chi-square tests and Fischer exact test were used for bivariate analysis. Multiple logistic regressions were used to elucidate the various risk factors influencing the presence and the severity of DR. Variables with a p value of <0.05 was included in a multivariate model. All hypotheses tests were based on two-sided test and p value <0.05 was considered statistically significant.

RESULT

Characteristic and Health Profile of the study population

Our study consisted of 738 eligible patients. T2DM accounted for 97% of cases (n=720). The age of our study population ranges from 19 to 82 years with the mean of 54±10 years. Almost all cases (98.7%) were aged above 30. The mean duration of DM among our patients was 5.52 (SD 5.8 years). More than half (55.8%) had DM for less than five years as summarised in Table 1.

Systemic hypertension was the most common co-morbidity found in our study population where 51.5% (n=380) has hypertension. About one third of the patients had sub-optimal control of hypertension (Table 1). In terms of glycaemic control, 75% (n=554) of the patients had sub-optimal HbA_1c level (Table 1). Majority of the patients did not achieve the targeted level of control for total cholesterol, LDL-cholesterol and triglyceride level (Table 1). Majority of patients, 85.6% (n=632) did not have proteinuria.  

Table 1: Characteristic and Health Profile of the respondents (n=738)

Variables	Frequency, n (%)
Total cholesterol
≤4.8 mmol/L	226 (30.6)
>4.8 mmol/L	512 (69.4)
TGL
≤1.7 mmol/L	345 (46.7)
>1.7 mmol/L	393 (53.3)
LDL
≤2.6 mmol/L	145 (19.6)
>2.6 mmol/L	593 (80.4)
HDL
>1.1 mmol/L	490 (66.4)
≤1.1 mmol/L	248 (33.6)
Present of coronary artery disease
Yes	12 (1.6)
No	726 (98.4)
Smoker
Yes	6 (0.8)
No	732 (99.2)
Visual loss
Normal 6/6	298 (40.4)
Mild 6/9 to 6/12	334 (45.3)
Moderate 6/18 to 6/60	106 (14.3)
Severe visual loss <6/60	0 (0)

Most of the patients (89.4%, n=660) had visual complaints, however, there were no patient with severe visual loss and blindness. 91.5% (n=675) were aware of DR. We found 175 out of the 738 cases (23.7%) to have DR changes. The majority of these, 86.2% (n=151) had non-proliferative retinopathy changes. Proliferative retinopathy changes were noted in 3.2% of the total patients screened. Maculopathy was seen in 2.7% (n=20).

Factors associated with diabetic retinopathy

Table 2 shows the present of DR and its association with different factors. Duration of diabetes, BMI, hypertension control and visual loss were found to be significantly associated with present of DR in the bivariate analysis. Factors like gender, ethnicity, glycaemic control, present of proteinuria and lipid profiles were not significantly associated with the present of DR. Statistical analysis was not done for age, present of coronary artery diseases, anaemia and smoking status, as the number of patients were too small for those with DR. Significance levels of the variables by multivariate analysis are presented in Table 3. The odds of developing DR was 2.5 times higher for a patient with duration of diagnosis between five to 10 years when compared to a patients with <5 years of diabetes. The odds of developing DR were increasing as the duration of diabetes increases.  Patients who were lean were more likely compared to obese and overweight to develop DR (OR=1.8). Moderate visual loss was associated with DR (OR=2.1). Multivariate logistric regression models for control of hypertension and separate analysis of systolic and diastolic BP found no significant association with the presence of DR.

Table 2: Prevalence of diabetic retinopathy and its association with different factors (Bivariate analysis between DR and non-DR)

Variables	Non-DR Frequency (N=563) (%)	DR Frequency (N=175) (%)	p value
Gender
Male	249 (78.5)	68 (21.5)	NS
Female	314 (74.6)	107 (25.4)
Ethnicity
Sarawak native	116 (80.0)	29 (20.0)	NS
Non-native	447 (75.4)	146 (24.6)
Duration of DM
<5 yrs	354 (85.9)	58 (14.1)	<0.001*
5-10 yrs	117 (70.9)	48 (29.1)
11-15 yrs	62 (62.0)	38 (38.0)
16-20 yrs	15 (50.0)	15 (50.0)
>20 yrs	15 (48.4)	16 (51.6)
Age in interval
19-29	9 (100.0)	0 (0)
30-39	34 (87.2)	5 (12.8)
40-49	139 (78.5)	38 (21.5)
50-59	217 (73.3)	79 (26.7)
60-69	118 (76.1)	37 (23.9)
70-79	46 (74.2)	16 (25.9)
BMI
<22.9	72 (64.9)	39 (35.1)	0.002*
≥23.0	491 (78.3)	136 (21.7)
HT control (mm/Hg)
Optimal <130/80	157 (80.1)	39 (19.9)	0.026*
Fair 130/80 to 140/90	221 (78.9)	59 (21.1)
Sub-optimal >140/90	185 (70.6)	77 (29.4)
HbA1c (%)
Optimal <6.5	69 (85.2)	12 (14.8)	NS
Fair 6.5-7.5	83 (80.6)	20 (19.4)
Sub-optimal >7.5	411 (74.2)	143 (25.8)
Protein in urine
Nil	491 (77.7)	141 (22.3)	NS
Microalbuminuria	14 (66.7)	7 (33.3)
Proteinuria	58 (68.2)	27 (31.8)
Total cholesterol
≤4.8 mmol/L	170 (75.2)	56 (24.7)	NS
>4.8 mmol/L	393 (76.8)	119 (23.2)
TGL
≤1.7 mmol/L	268 (77.7)	77 (22.3)	NS
>1.7 mmol/L	295 (75.1)	98 (24.9)
LDL
≤2.6 mmol/L	115 (79.3)	30 (20.7)	NS
>2.6 mmol/L	448 (75.5)	145 (24.5)
HDL
>1.1 mmol/L	376 (76.7)	114 (23.3)	NS
≤1.1 mmol/L	187 (75.4)	61 (24.6)
Present of coronary artery disease
Yes	11 (91.7)	1 ( 8.3)	-
No	552 (76.0)	174 (24.0)
Smokers
Yes	4 (66.7)	2 (33.3)	-
No	559 (76.4)	173 (23.7)
Visual loss
Normal 6/6	241 (80.9)	57 (19.1)	0.001*
Mild 6/9 to 6/12	256 (76.6)	78 (23.4)
Moderate 6/18 to 6/60	66 (62.3)	40 (37.7)

* p-value significant from bivariate analysis NS= not significant