Letters
In addition, to optimize the sensitivity and specificity for predicting future diabetes, the American Diabetes Association lowered the fasting glucose cut point from 110 mg/dL to 100 mg/dL for the diagnosis of impaired fasting glucose in their 2003 guidelines.6 This criterion has been widely accepted and used. Yufang Bi, MD, PhD Yu Xu, PhD Guang Ning, MD, PhD Author Affiliations: Key Laboratory for Endocrine and Metabolic Diseases of Ministry of Health, Rui-Jin Hospital, Shanghai, China. Corresponding Author: Guang Ning, MD, PhD, Rui-Jin Hospital, 197 Rui-Jin 2nd Rd, Shanghai 200025, China ([email protected]). Conflict of Interest Disclosures: The authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest and none were reported. 1. Li LM, Rao KQ, Kong LZ, et al; Technical Working Group of China National Nutrition and Health Survey. A description on the Chinese national nutrition and health survey in 2002 [in Chinese]. Zhonghua Liu Xing Bing Xue Za Zhi. 2005;26(7):478-484.
of headache less likely to be subarachnoid hemorrhage in their sample, resulting in an estimated sensitivity that may be higher than what would be expected in a routine clinic. They recommended use of the OSHR be restricted to patients with similar characteristics.1 However, this spectrum effect may also be related to lower reliability. Specifically, a homogeneous sample of patients would have less variability, and as variability decreases so does the ability to use the OSHR in different patient groups over time (ie, reliability).3 Although developing and restricting clinical decision rule use for patients with a narrow spectrum of disease is appealing because it may lead to improved sensitivity, repeated application of the OSHR may reveal poorer performance over time. One would expect that the risk of misclassification of important characteristics such as thunderclap headache would be high in this OSHR, and thus, even if applied precisely,4 the rule may not perform as well as expected at different centers.5 Development of formal training criteria may be necessary before its widespread use.
2. Yang W, Lu J, Weng J, et al; China National Diabetes and Metabolic Disorders Study Group. Prevalence of diabetes among men and women in China. N Engl J Med. 2010;362(12):1090-1101.
Adrian V. Specogna, MSc, PhD
3. American Diabetes Association. Diagnosis and classification of diabetes mellitus. Diabetes Care. 2010;33(suppl 1):S62-S69.
Author Affiliation: Department of Community Health Sciences, University of Calgary, Calgary, Alberta, Canada.
4. Sabanayagam C, Liew G, Tai ES, et al. Relationship between glycated haemoglobin and microvascular complications: is there a natural cut-off point for the diagnosis of diabetes? Diabetologia. 2009;52(7):1279-1289.
Corresponding Author: Adrian V. Specogna, MSc, PhD, University of Calgary, 3280 Hospital Dr NW, Calgary, AB T2N 4Z6, Canada ([email protected]).
5. Heianza Y, Hara S, Arase Y, et al. HbA1c 5·7-6·4% and impaired fasting plasma glucose for diagnosis of prediabetes and risk of progression to diabetes in Japan (TOPICS 3): a longitudinal cohort study. Lancet. 2011;378(9786):147-155. 6. Genuth S, Alberti KG, Bennett P, et al; Expert Committee on the Diagnosis and Classification of Diabetes Mellitus. Follow-up report on the diagnosis of diabetes mellitus. Diabetes Care. 2003;26(11):3160-3167.
Subarachnoid Hemorrhage Diagnosis To the Editor In their recent study, Dr Perry and colleagues1 addressed the challenging problem of misdiagnosis of subarachnoid hemorrhage. Perry et al1 reported 100% sensitivity for detecting subarachnoid hemorrhage, using the new Ottawa subarachnoid hemorrhage rule (OSHR). Despite this finding, 3 of the 6 characteristics in the rule showed only modest reliability (κ
In addition, to optimize the sensitivity and specificity for predicting future diabetes, the American Diabetes Association lowered the fasting glucose cut point from 110 mg/dL to 100 mg/dL for the diagnosis of impaired fasting glucose in their 2003 guidelines.6 This criterion has been widely accepted and used. Yufang Bi, MD, PhD Yu Xu, PhD Guang Ning, MD, PhD Author Affiliations: Key Laboratory for Endocrine and Metabolic Diseases of Ministry of Health, Rui-Jin Hospital, Shanghai, China. Corresponding Author: Guang Ning, MD, PhD, Rui-Jin Hospital, 197 Rui-Jin 2nd Rd, Shanghai 200025, China ([email protected]). Conflict of Interest Disclosures: The authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest and none were reported. 1. Li LM, Rao KQ, Kong LZ, et al; Technical Working Group of China National Nutrition and Health Survey. A description on the Chinese national nutrition and health survey in 2002 [in Chinese]. Zhonghua Liu Xing Bing Xue Za Zhi. 2005;26(7):478-484.
of headache less likely to be subarachnoid hemorrhage in their sample, resulting in an estimated sensitivity that may be higher than what would be expected in a routine clinic. They recommended use of the OSHR be restricted to patients with similar characteristics.1 However, this spectrum effect may also be related to lower reliability. Specifically, a homogeneous sample of patients would have less variability, and as variability decreases so does the ability to use the OSHR in different patient groups over time (ie, reliability).3 Although developing and restricting clinical decision rule use for patients with a narrow spectrum of disease is appealing because it may lead to improved sensitivity, repeated application of the OSHR may reveal poorer performance over time. One would expect that the risk of misclassification of important characteristics such as thunderclap headache would be high in this OSHR, and thus, even if applied precisely,4 the rule may not perform as well as expected at different centers.5 Development of formal training criteria may be necessary before its widespread use.
2. Yang W, Lu J, Weng J, et al; China National Diabetes and Metabolic Disorders Study Group. Prevalence of diabetes among men and women in China. N Engl J Med. 2010;362(12):1090-1101.
Adrian V. Specogna, MSc, PhD
3. American Diabetes Association. Diagnosis and classification of diabetes mellitus. Diabetes Care. 2010;33(suppl 1):S62-S69.
Author Affiliation: Department of Community Health Sciences, University of Calgary, Calgary, Alberta, Canada.
4. Sabanayagam C, Liew G, Tai ES, et al. Relationship between glycated haemoglobin and microvascular complications: is there a natural cut-off point for the diagnosis of diabetes? Diabetologia. 2009;52(7):1279-1289.
Corresponding Author: Adrian V. Specogna, MSc, PhD, University of Calgary, 3280 Hospital Dr NW, Calgary, AB T2N 4Z6, Canada ([email protected]).
5. Heianza Y, Hara S, Arase Y, et al. HbA1c 5·7-6·4% and impaired fasting plasma glucose for diagnosis of prediabetes and risk of progression to diabetes in Japan (TOPICS 3): a longitudinal cohort study. Lancet. 2011;378(9786):147-155. 6. Genuth S, Alberti KG, Bennett P, et al; Expert Committee on the Diagnosis and Classification of Diabetes Mellitus. Follow-up report on the diagnosis of diabetes mellitus. Diabetes Care. 2003;26(11):3160-3167.
Subarachnoid Hemorrhage Diagnosis To the Editor In their recent study, Dr Perry and colleagues1 addressed the challenging problem of misdiagnosis of subarachnoid hemorrhage. Perry et al1 reported 100% sensitivity for detecting subarachnoid hemorrhage, using the new Ottawa subarachnoid hemorrhage rule (OSHR). Despite this finding, 3 of the 6 characteristics in the rule showed only modest reliability (κ
