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Value of humerus length shortening for prenatal detection of Down syndrome in a Thai population
Author(s) -
Tannirandorn Yuen,
Manotaya Saknan,
Uerpairojkit Boonchai,
Tanawattanacharoen Somchai,
Wacharaprechat Teera,
Charoenvidhya Dhiraphongs
Publication year - 2002
Publication title -
journal of obstetrics and gynaecology research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.597
H-Index - 50
eISSN - 1447-0756
pISSN - 1341-8076
DOI - 10.1046/j.1341-8076.2002.00013.x
Subject(s) - medicine , humerus , amniocentesis , population , receiver operating characteristic , confidence interval , likelihood ratios in diagnostic testing , down syndrome , obstetrics , prenatal diagnosis , fetus , pregnancy , surgery , biology , environmental health , psychiatry , genetics
Objective: To assess the value of humerus length shortening for prenatal detection of Down syndrome in a Thai population. Methods: A prospective study was performed on 3053 women undergoing second‐trimester amniocentesis, between 16 and 24 weeks gestation, for the indications of advanced maternal age and a past history of chromosomal abnormality. Biparietal diameter (BPD) and humerus length measurements were obtained before the procedures. Regression equations relating BPD to humerus length were used to calculate observed humerus length/expected humerus length ratio in chromosomally normal and Down syndrome fetuses. Sensitivity, specificity, false‐positive rate and likelihood ratio of a positive test result at various observed humerus length/expected humerus length ratios for detection of Down syndrome were calculated. A receiver–operator characteristic curve was used to determine the threshold screening ratio. Results: There were 3003 chromosomally normal pregnancies and 24 fetuses with Down syndrome. The relationship between humerus length and BPD was: expected humerus length = 0.7403BPD – 5.1057, R 2 = 0.77, P < 0.001. Humerus length in Down syndrome fetuses was significantly shorter than in normal fetuses ( P < 0.001). A ratio of 0.91 for observed humerus length/expected humerus length yielded a sensitivity of 41.7%, specificity of 88.3%, a false‐positive rate of 11.7% and likelihood ratio of a positive test result of 3.63 (95% confidence interval 2.24–5.88) for detection of Down syndrome. Conclusions Humerus length shortening in the second trimester appears to be a useful adjunctive screening parameter for fetal Down syndrome in a Thai population.