Diabetes in Oman

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Diabetes in Oman: Comparison of 1997 American

Diabetes Association Classification of Diabetes

Mellitus with 1985 WHO classification

Jawad A. Al-Lawati, MD, MPH; Ali J. Mohammed, MD, MSc

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Background: Diabetes mellitus (DM) is a major public health problem in Oman. We evaluated the impact of the revised diagnostic criteria for DM adopted by the American Diabetes Association (ADA) on the prevalence of diabetes and impaired glucose tolerance (IGT), and on the classification of individuals among the Omani population.
Subjects and Methods: We used the dataset of the National Diabetes Survey, conducted in 1991 and involving 4682 subjects who did not have any missing data on fasting and 2-hour glucose. The subjects comprised 2002 males and 2680 females aged 20 years or above. Data were analyzed using the ADA criteria (diabetes as fasting plasma glucose [FPG] ³ 7 mmol/L, impaired fasting glucose [IFG] as FPG ³ 6.1 mmol/L and <7 mmol/L), and compared these with the World Health Organization (WHO) criteria (diabetes as FPG ³ 7.8 mmol/L and/or 2-hour post-glucose load ³ 11.1 mmol/L, IGT as FPG <7.8 mmol/L, and 2-hour post-load 7.8-11.1 mmol/L).
Results: Applying the ADA criteria on the Omani population resulted in an overall reduction of diabetes prevalence by 2.2% (95% confidence interval [CI] 1.6% to 2.8%), and a 4.8% reduction of IGT (95% CI 3.8% to 5.8%). Over 29% of diabetics classified by the WHO criteria were reclassified as being normal or having IFG by the ADA criteria. Around 3.6% of those who were normoglycemic by the WHO criteria were classified as having diabetes or IFG by the ADA criteria. In all but one region of Oman, the prevalence of diabetes and IFG using the ADA criteria was lower compared to the prevalence using the WHO criteria. Gender, age and body mass index did not seem to pose an increased risk to the probability of being diagnosed by one criteria or the other or both together.
Conclusion: The adoption of the ADA criteria in Oman will significantly reduce the prevalence of diabetes and IGT. In addition, the glycemic status of a substantial number of individuals will be changed from normal to either being diabetic or having IGT

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Ann Saudi Med 2000;20(1):12-15.

 
Diabetes mellitus (DM) is a major public health problem world-wide. In 1997, the World Health Organization (WHO) estimated its global prevalence to be more than 135 million, and projections for the year 2025 estimate a 120% increase in the number of people with diabetes throughout the world.1 Diabetes, predominantly non-insulin dependent diabetes mellitus (NIDDM), is also a significant public health problem in the Sultanate of Oman. In 1991, the Ministry of Health, in collaboration with the WHO, conducted a national survey to estimate the burden of DM and other cardiovascular disease risk factors in Oman. This survey, using the WHO recommended methodology and diagnostic criteria,2 showed that 10% of the Omani
From the Non-Communicable Diseases Section (Dr. Al-Lawati) and Health Affairs (Dr. Mohammed), Ministry of Health, Muscat, Oman.
Address reprint requests and correspondence to Dr. Al-Lawati: Non-Communicable Diseases Section, Ministry of Health, P.O. Box 393, Muscat 113, Oman.
Accepted for publication 13 November 1999. Received 21 June 1999.
population aged 20 years or above have diabetes mellitus.3 A further 10% was shown to have impaired glucose tolerance (IGT).
In 1997, the American Diabetes Association (ADA) adopted the recommendations put forward by an Expert Committee on the Diagnosis and Classification of Diabetes Mellitus,4 which included modification of the diagnostic criteria suggested earlier by the National Diabetes Data Group5 and WHO.6 The new criteria suggest that for epidemiological studies of incidence and prevalence, a fasting plasma glucose of ³ 7 mmol/L (126 mg/dL) could be used alone4 compared to the 2-hour post-glucose load value of ³ 11.1 mmol/L (200 mg/dL) suggested by WHO for the diagnosis of diabetes mellitus.
These recent changes in the diagnostic criteria may have an impact on the prevalence rates in Oman, and subsequently on the planning process and the cost incurred to the health services for the management of this chronic condition. In addition, it may have bearing on the reclassification of individuals,7,8 as those with diabetes

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TABLE 1. Comparison of WHO and ADA diagnostic criteria.
    1997 ADA Criteria**   
1985 WHO Criteria*   Normal   IFG   Diabetes   WHO total (% prevalence)
Normal   3566   115   17   3698 (79%)
Row %   96.4   3.1   0.46   
Column %   88.6   43   4.4   
IGT   385   82   26   493 (10.5%)
Row %   78.1   16.6   5.3   
Column %   9.6   30.6   6.7   
Diabetes   75   71   345   491 (10.5%)
Row %   15.3   14.5   70.3   
Column %   1.9   26.5   89   
ADA total (% prevalence)   4026(86%)   268(5.7%)   388(8.3%)   4682
*WHO criteria: diabetes as FPG ³ 7.8 mmol/L and/or 2-hour post-load ³ 11.1 mmol/L; IGT as FPG < 7.8 mmol/L and 2-hour post-load 7.8-11.1 mmol/L; normal as FPG < 7.8 mmol/L and 2-hour post-load <7.8 mmol/L.**ADA criteria: diabetes as FPG ³ 7 mmol/L; impaired fasting glucose (IFG) ³ 6.1 mmol/L and < 7 mmol/L; normal as FPG < 6.1 mmol/L.

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TABLE 2. Selected factors associated with disagreement of classification between WHO and ADA criteria for diagnosis of diabetes (numbers and percentage of subjects).
Variable   WHO criteriaonly (n=491)    ADA criteriaonly (n=388)   WHO and ADA criteria (n=345)   P- Value=
Sex               
Men (n=539)   209 (38)   178 (33)   152 (28)   0.618
Women (n=685)   282 (41)   210 (31)   193 (28)   
Age (years)*               
< 50 (n=640)   255 (40)   206 (32)   179 (28)   0.715
50-64 (n=445)   173 (39)   142 (32)   130 (29)   
³ 65 (n=388)   62 (16)   39 (1)   35 (9)   
BMI (kg/m2)**               
< 25 (n=388)   154 (40)   125 (32)   109 (28)   0.945
25-30 (n=440)   172 (39)   143 (32)   125 (28)   
³ 30 (n=396)   165 (42)   120 (30)   111 (28)   
See footnote to Table 1 for diagnostic criteria of the WHO and ADA; *Missing for one; **BMI=body mass index=weight/height2 (kg/m2); = c 2 test.
according to the WHO criteria may be reclassified as normal or with impaired fasting glucose (IFG) by the ADA criteria and vice versa. In this report, we attempt to evaluate the impact of the new diagnostic criteria of diabetes mellitus and impaired glucose categories on the overall national and regional prevalence rates, based on reanalysis of the 1991 epidemiological survey.