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Screening for gestational diabetes in a high-risk population using fasting plasma glucose
International Journal of Gynecology & Obstetrics 68 Ž2000. 147᎐148
Brief communication
Screening for gestational diabetes in a high-risk population using fasting plasma glucose M.M. Agarwala,U , P.F. Hughes b, M. Ezimokhai b a
Department of Pathology, Faculty of Medicine, U.A.E. Uni¨ ersity, Al Ain, United Arab Emirates Obstetrics & Gynecology, Faculty of Medicine, U.A.E. Uni¨ ersity, Al Ain, United Arab Emirates
b
Received 23 June 1999; received in revised form 8 October 1999; accepted 4 November 1999
Keywords: Gestational diabetes; Screening; Fasting glucose
Gestational diabetes ŽGDM. is a controversial condition without consensus on whether screening is justified, the ideal way to screen, and how to best manage it following diagnosis w1x. The approach of the American Diabetes Association is widely accepted in North America, i.e. a nonfasting post 50 g, 1-h plasma glucose screen ŽGCT. followed by the confirmatory ‘gold standard’ 100 g, 3-h oral glucose tolerance test ŽoGTT. for positive screens w2x. In the United Arab Emirates ŽUAE., due to a very high prevalence of GDM w3x, the recommended practice of universal screening in highrisk populations with a GCT makes excessive demands on the health delivery system. We report the potential value of fasting blood glucose
U
Corresponding author. Tel.: q971-3-5039-467; fax: q9713-671966. E-mail address: [email protected] ŽM.M. Agarwal.
ŽFBS. as an alternative screening test in our population. A total of 430 subjects who were referred for an oGTT were available for the study, 93 patients were GCT screen-positive with the remaining 337 patients being tested on clinical grounds. The major ethnic distribution of the study population comprised nationals of the Indian subcontinent Ž29.1%., Arabs from Jordan, Lebanon and Syria Ž18.8%., UAE Ž19.1%., North Africa Ž14.2%., and East Africa Ž8.4%.. Standard GCT and oGTT protocols were used and the data were analyzed using the SAS statistical program. GDM diagnosis was based on Carpenter’s modified criteria by which 116 Ž27%. patients were classified as having GDM. We used the rule in and rule out strategy w4x to analyze the value of FBS as a screening test. This involves considering two cutoff values; the higher value which has an increased specificity is used to rule in the disease
0020-7292r00r$20.00 䊚 2000 International Federation of Gynecology and Obstetrics. PII: S 0 0 2 0 - 7 2 9 2 Ž 9 9 . 0 0 2 0 1 - 5
148
M.M. Agarwal et al. r International Journal of Gynecology & Obstetrics 68 (2000) 147᎐148
Table 1 Selected threshold values of fasting plasma glucose Ž n s 430. with associated test sensitivity, specificity, positive ŽPPV q . and negative ŽNPVy . predictive values; and likelihood ratios of positive ŽLR q . and negative ŽLR y . test result Threshold mmolrl Žmgrdl. G
3.9 Ž70.
4.2 Ž75.
4.4 Ž80.
4.7 Ž85.
5.0 Ž90.
5.3 Ž95.
5.6 Ž100.
5.8 Ž105.
Sensitivity Ž%. Specificity Ž%. PPV q Ž%. NPVy Ž%. LR q LR᎐
95.7 20.7 30.8 92.9 1.21 0.21
93.1 38.5 35.9 93.8 1.51 0.18
87.1 61.2 45.3 92.8 2.24 0.21
72.4 80.6 57.9 88.8 3.73 0.34
62.9 89.5 68.9 86.7 5.99 0.41
48.3 97.5 87.5 83.6 18.95 0.53
30.6 98.7 89.5 80.1 24.05 0.70
27.6 98.7 88.9 78.7 21.66 0.73
under consideration, while the lower cut-off value with its inherent increased sensitivity is used to rule out the disease in question. Using a FBS value G 5.3 mmolrl Ž95 mgrdl. as the higher FBS threshold to rule in GDM Žwith a specificity of 97.5% and the log likelihood ratio of 18.9. ŽTable 1. would have eliminated the oGTT in 64 of 430 patients Ž14.9%.. Using a lower FBS cut-off of - 4.2 mmolrl Ž75 mgrdl. to rule out GDM, with a sensitivity of 93%, 129 patients would not need an oGTT Ž30%.. Thus, the fasting glucose alone would have eliminated the need for nearly 45% of the oGTTs, with only 16 patients Ž3.7%. being misclassified. This simple approach, though not universally applicable, could be meaningful in selected very high prevalence popula-
tions by being clinically useful, cost-effective and patient-friendly. References w1x Greene MF. Screening for gestational diabetes mellitus. N Engl J Med 1997;337:1625᎐1626. w2x Metzger BE, Coustan DR. Summary and recommendations of the fourth international workshop-conference on gestational diabetes mellitus. Diabetes Care 1998; 21ŽSuppl. 2.:161᎐167. w3x Hughes PF, Agarwal M, Newman P, Morrison J. An evaluation of fructosamine estimation in screening for gestational diabetes mellitus. Diabetic Med 1995; 12:708᎐712. w4x Henderson AR. Assessing test accuracy and its clinical consequences: a primer for receiver operating characteristic curve analysis. Ann Clin Biochem 1993;30:521᎐539.
Brief communication
Screening for gestational diabetes in a high-risk population using fasting plasma glucose M.M. Agarwala,U , P.F. Hughes b, M. Ezimokhai b a
Department of Pathology, Faculty of Medicine, U.A.E. Uni¨ ersity, Al Ain, United Arab Emirates Obstetrics & Gynecology, Faculty of Medicine, U.A.E. Uni¨ ersity, Al Ain, United Arab Emirates
b
Received 23 June 1999; received in revised form 8 October 1999; accepted 4 November 1999
Keywords: Gestational diabetes; Screening; Fasting glucose
Gestational diabetes ŽGDM. is a controversial condition without consensus on whether screening is justified, the ideal way to screen, and how to best manage it following diagnosis w1x. The approach of the American Diabetes Association is widely accepted in North America, i.e. a nonfasting post 50 g, 1-h plasma glucose screen ŽGCT. followed by the confirmatory ‘gold standard’ 100 g, 3-h oral glucose tolerance test ŽoGTT. for positive screens w2x. In the United Arab Emirates ŽUAE., due to a very high prevalence of GDM w3x, the recommended practice of universal screening in highrisk populations with a GCT makes excessive demands on the health delivery system. We report the potential value of fasting blood glucose
U
Corresponding author. Tel.: q971-3-5039-467; fax: q9713-671966. E-mail address: [email protected] ŽM.M. Agarwal.
ŽFBS. as an alternative screening test in our population. A total of 430 subjects who were referred for an oGTT were available for the study, 93 patients were GCT screen-positive with the remaining 337 patients being tested on clinical grounds. The major ethnic distribution of the study population comprised nationals of the Indian subcontinent Ž29.1%., Arabs from Jordan, Lebanon and Syria Ž18.8%., UAE Ž19.1%., North Africa Ž14.2%., and East Africa Ž8.4%.. Standard GCT and oGTT protocols were used and the data were analyzed using the SAS statistical program. GDM diagnosis was based on Carpenter’s modified criteria by which 116 Ž27%. patients were classified as having GDM. We used the rule in and rule out strategy w4x to analyze the value of FBS as a screening test. This involves considering two cutoff values; the higher value which has an increased specificity is used to rule in the disease
0020-7292r00r$20.00 䊚 2000 International Federation of Gynecology and Obstetrics. PII: S 0 0 2 0 - 7 2 9 2 Ž 9 9 . 0 0 2 0 1 - 5
148
M.M. Agarwal et al. r International Journal of Gynecology & Obstetrics 68 (2000) 147᎐148
Table 1 Selected threshold values of fasting plasma glucose Ž n s 430. with associated test sensitivity, specificity, positive ŽPPV q . and negative ŽNPVy . predictive values; and likelihood ratios of positive ŽLR q . and negative ŽLR y . test result Threshold mmolrl Žmgrdl. G
3.9 Ž70.
4.2 Ž75.
4.4 Ž80.
4.7 Ž85.
5.0 Ž90.
5.3 Ž95.
5.6 Ž100.
5.8 Ž105.
Sensitivity Ž%. Specificity Ž%. PPV q Ž%. NPVy Ž%. LR q LR᎐
95.7 20.7 30.8 92.9 1.21 0.21
93.1 38.5 35.9 93.8 1.51 0.18
87.1 61.2 45.3 92.8 2.24 0.21
72.4 80.6 57.9 88.8 3.73 0.34
62.9 89.5 68.9 86.7 5.99 0.41
48.3 97.5 87.5 83.6 18.95 0.53
30.6 98.7 89.5 80.1 24.05 0.70
27.6 98.7 88.9 78.7 21.66 0.73
under consideration, while the lower cut-off value with its inherent increased sensitivity is used to rule out the disease in question. Using a FBS value G 5.3 mmolrl Ž95 mgrdl. as the higher FBS threshold to rule in GDM Žwith a specificity of 97.5% and the log likelihood ratio of 18.9. ŽTable 1. would have eliminated the oGTT in 64 of 430 patients Ž14.9%.. Using a lower FBS cut-off of - 4.2 mmolrl Ž75 mgrdl. to rule out GDM, with a sensitivity of 93%, 129 patients would not need an oGTT Ž30%.. Thus, the fasting glucose alone would have eliminated the need for nearly 45% of the oGTTs, with only 16 patients Ž3.7%. being misclassified. This simple approach, though not universally applicable, could be meaningful in selected very high prevalence popula-
tions by being clinically useful, cost-effective and patient-friendly. References w1x Greene MF. Screening for gestational diabetes mellitus. N Engl J Med 1997;337:1625᎐1626. w2x Metzger BE, Coustan DR. Summary and recommendations of the fourth international workshop-conference on gestational diabetes mellitus. Diabetes Care 1998; 21ŽSuppl. 2.:161᎐167. w3x Hughes PF, Agarwal M, Newman P, Morrison J. An evaluation of fructosamine estimation in screening for gestational diabetes mellitus. Diabetic Med 1995; 12:708᎐712. w4x Henderson AR. Assessing test accuracy and its clinical consequences: a primer for receiver operating characteristic curve analysis. Ann Clin Biochem 1993;30:521᎐539.