NEWS & VIEWS COELIAC DISEASE
Missing villi? The search for coeliac disease in the Asia–Pacific region Thimmaiah G. Theethira and Ciarán P. Kelly
Epidemiology studies have shown an ~1% prevalence of coeliac disease in Europe, North America, the Middle East and South America, but the prevalence in the Asia–Pacific region remains relatively unknown. Now, Makharia et al. have proposed much needed recommendations to help tackle the problem of coeliac disease in this region. Theethira, T. G. & Kelly, C. P. Nat. Rev. Gastroenterol. Hepatol. 11, 204–205 (2014); published online 25 February 2014; doi:10.1038/nrgastro.2013.26
Coeliac disease is a chronic immunemediated enteropathy precipitated by exposure to dietary gluten in genetically predisposed individuals (that is, those who are positive for the HLA-DQ2 or HLA-DQ8 haplotypes). Gluten is the commonly used term for the complex of water-insoluble proteins from wheat, rye and barley that are harmful to patients with coeliac disease. Epidemiological surveys in Europe and in the USA have revealed that coeliac disease has a prevalence of ~1%, with regional variation in Europe (including 0.3% in Germany and 2.4% in Finland).1,2 Studies from the past few years also indicate that coeliac disease is not confined to Europe and North America, but is found with similar prevalence in North Africa, the Middle East and South America.3,4 However, the prevalence of coeliac disease in the Asia–Pacific region remains largely unknown (Figure 1) with a dearth of reliable, population-based data.5 A notable exception is India, where coeliac disease has been well recognized, especially in the Northern area, for several decades. A study published in 2011 showed that the overall prevalence of coeliac disease was 1% in Northern India, similar to that in Europe and North America.6 In an attempt to overcome the lacuna of information on coeliac disease prevalence in Asia, Makharia et al. 7 have taken a much needed initiative in describing the deficit and making recommendations for future studies. Makharia et al. 7 note that substantial variation seems to exist in the prevalence of coeliac disease among countries in the Asia–Pacific region. Northern India, Australia and New Zealand seem to have a
‘‘
…the prevalence of coeliac disease in the Asia–Pacific region remains largely unknown…
’’
very similar prevalence to Western Europe and North America. In India, the prevalence seems to decrease from North to South; this difference parallels wheat consumption, which transitions from a wheat-based diet in the Northern belt to a rice-based diet in the South. However, one study noted an increased prevalence of coeliac disease in children born in Northern India who had settled in the South.8 This finding might indicate additional risk factors (such as genetic variations) that contribute to this ‘North–South’ Indian imbalance. Testing for coeliac disease in the Asia– Pacific region also deserves special attention. Inexpensive, point-of-care tests for tissue transglutaminase‑2 IgA (TTG) are likely to be popular, especially in countries with limited health resources. Those patients who test positive on point-of-care tests might have the results confirmed by conventional coeliac serology. However, the cut-off values for these assays are derived from Western European populations; currently, no data are available for cut-off values for Asian populations. This gap needs to be filled before reliable population prevalence data can be obtained. Makharia et al.7 also refer to an interesting observation that tropical enteropathy leads to a reduction in the ratio of average villous height to crypt depth in some Asian populations. Such differences indicate further complexities in diagnosing coeliac disease in the Asia–Pacific region.
NATURE REVIEWS | GASTROENTEROLOGY & HEPATOLOGY © 2014 Macmillan Publishers Limited. All rights reserved
Regarding genetic testing, it has been shown that the absence of the HLA-DQ2 and HLA-DQ8 haplotypes has a very high negative predictive value for coeliac disease in white European populations.9 However, it is unknown whether other HLA types or other genetic traits might be associated with coeliac disease in Asian nations. Compounding these unknowns is the fact that awareness of coeliac disease and the techniques used for diagnosis are low amongst general practitioners in Europe and North America and are probably even lower amongst health-care providers in the Asia–Pacific countries. As an example, a publication from 2012 from Pakistan described what was purported to be the first ever case of biopsy-proven coeliac disease in adults from that country.10 Makharia et al.7 have taken a step in the right direction in drawing attention to this hidden and unquantified health problem in the Asia–Pacific region. On the basis of experiences in North America, South America, North Africa, the Middle East and India, it is quite possible that studies might unearth a substantial and hitherto unknown group of people with coeliac disease in the Asia–Pacific region. The potential barriers to overcoming this new health problem will be substantially different to those encountered in Western populations. Some of the key issues worthy of consideration include the development of low cost, subsidized, serology assays (including point-of-care testing),
1:50–1:500 1:500–1:20,000
Missing villi? The search for coeliac disease in the Asia–Pacific region Thimmaiah G. Theethira and Ciarán P. Kelly
Epidemiology studies have shown an ~1% prevalence of coeliac disease in Europe, North America, the Middle East and South America, but the prevalence in the Asia–Pacific region remains relatively unknown. Now, Makharia et al. have proposed much needed recommendations to help tackle the problem of coeliac disease in this region. Theethira, T. G. & Kelly, C. P. Nat. Rev. Gastroenterol. Hepatol. 11, 204–205 (2014); published online 25 February 2014; doi:10.1038/nrgastro.2013.26
Coeliac disease is a chronic immunemediated enteropathy precipitated by exposure to dietary gluten in genetically predisposed individuals (that is, those who are positive for the HLA-DQ2 or HLA-DQ8 haplotypes). Gluten is the commonly used term for the complex of water-insoluble proteins from wheat, rye and barley that are harmful to patients with coeliac disease. Epidemiological surveys in Europe and in the USA have revealed that coeliac disease has a prevalence of ~1%, with regional variation in Europe (including 0.3% in Germany and 2.4% in Finland).1,2 Studies from the past few years also indicate that coeliac disease is not confined to Europe and North America, but is found with similar prevalence in North Africa, the Middle East and South America.3,4 However, the prevalence of coeliac disease in the Asia–Pacific region remains largely unknown (Figure 1) with a dearth of reliable, population-based data.5 A notable exception is India, where coeliac disease has been well recognized, especially in the Northern area, for several decades. A study published in 2011 showed that the overall prevalence of coeliac disease was 1% in Northern India, similar to that in Europe and North America.6 In an attempt to overcome the lacuna of information on coeliac disease prevalence in Asia, Makharia et al. 7 have taken a much needed initiative in describing the deficit and making recommendations for future studies. Makharia et al. 7 note that substantial variation seems to exist in the prevalence of coeliac disease among countries in the Asia–Pacific region. Northern India, Australia and New Zealand seem to have a
‘‘
…the prevalence of coeliac disease in the Asia–Pacific region remains largely unknown…
’’
very similar prevalence to Western Europe and North America. In India, the prevalence seems to decrease from North to South; this difference parallels wheat consumption, which transitions from a wheat-based diet in the Northern belt to a rice-based diet in the South. However, one study noted an increased prevalence of coeliac disease in children born in Northern India who had settled in the South.8 This finding might indicate additional risk factors (such as genetic variations) that contribute to this ‘North–South’ Indian imbalance. Testing for coeliac disease in the Asia– Pacific region also deserves special attention. Inexpensive, point-of-care tests for tissue transglutaminase‑2 IgA (TTG) are likely to be popular, especially in countries with limited health resources. Those patients who test positive on point-of-care tests might have the results confirmed by conventional coeliac serology. However, the cut-off values for these assays are derived from Western European populations; currently, no data are available for cut-off values for Asian populations. This gap needs to be filled before reliable population prevalence data can be obtained. Makharia et al.7 also refer to an interesting observation that tropical enteropathy leads to a reduction in the ratio of average villous height to crypt depth in some Asian populations. Such differences indicate further complexities in diagnosing coeliac disease in the Asia–Pacific region.
NATURE REVIEWS | GASTROENTEROLOGY & HEPATOLOGY © 2014 Macmillan Publishers Limited. All rights reserved
Regarding genetic testing, it has been shown that the absence of the HLA-DQ2 and HLA-DQ8 haplotypes has a very high negative predictive value for coeliac disease in white European populations.9 However, it is unknown whether other HLA types or other genetic traits might be associated with coeliac disease in Asian nations. Compounding these unknowns is the fact that awareness of coeliac disease and the techniques used for diagnosis are low amongst general practitioners in Europe and North America and are probably even lower amongst health-care providers in the Asia–Pacific countries. As an example, a publication from 2012 from Pakistan described what was purported to be the first ever case of biopsy-proven coeliac disease in adults from that country.10 Makharia et al.7 have taken a step in the right direction in drawing attention to this hidden and unquantified health problem in the Asia–Pacific region. On the basis of experiences in North America, South America, North Africa, the Middle East and India, it is quite possible that studies might unearth a substantial and hitherto unknown group of people with coeliac disease in the Asia–Pacific region. The potential barriers to overcoming this new health problem will be substantially different to those encountered in Western populations. Some of the key issues worthy of consideration include the development of low cost, subsidized, serology assays (including point-of-care testing),
1:50–1:500 1:500–1:20,000
