Westerway Susan Campbell, Pedersen Lars Henning, Hyett Jon
Northern Women's ImagingSydneyNew South WalesAustralia; Discipline of Obstetrics Gynaecology and NeonatologyFaculty of MedicineUniversity of SydneySydneyNew South WalesAustralia.
Department of Obstetrics and GynaecologyInstitute of Clinical MedicineAarhus UniversityAarhusDenmark; RPA Women and BabiesRoyal Prince Alfred HospitalSydneyNew South WalesAustralia.
Australas J Ultrasound Med. 2015 Feb;18(1):19-26. doi: 10.1002/j.2205-0140.2015.tb00019.x. Epub 2015 Dec 31.
: To compare transabdominal (TA) and transvaginal (TV) ultrasound assessment of cervical length at 16-41 weeks gestation. : TA and TV ultrasound measurements of cervical length were made on 491 pregnancies of 16-41 weeks gestation. Cervical length was measured from internal to external cervical os. Bland-Altman plots and Wilcoxon signed rank test were used to evaluate differences between TA and TV measurements. : The validity of the TA method depended on cervical length. Although the TA method underestimated cervical length by 2.0 mm on average ( < 0.001), Bland Altman plots showed an inverse trend with shorter cervixes. In women with a cervix < 25 mm (n = 30) based on TV scan measurement, TA overestimated cervical length by 12 mm (P < 0.001). The sensitivity and specificity of TA as a test to detect cervical length < 25 mm were 10% (95% CI: 2.1-26%) and 94% (95% CI: 92-96%) respectively; the negative LR was 0.96 (95% CI: 0.84-1.08). The maximum area under the ROC curve would be obtained at a TA cut-off = 32 mm (to detect a cervix < 25 mm), corresponding to a sensitivity of 77% and a specificity of 58%. : TA measurements do not reflect TV assessment accurately, particularly if the cervix is short. At 24-34 weeks, a policy of proceeding to TV scan if TA measurement is < 25 mm will only detect 10% of affected pregnancies and has a poor positive predictive value so is of limited value as a predictive tool for women attending with symptoms and signs of preterm labour > 24 weeks gestation. There is no value in TA assessment of the cervix > 36 weeks.
比较孕16 - 41周经腹（TA）和经阴道（TV）超声测量宫颈长度的情况。对491例孕16 - 41周的孕妇进行TA和TV超声测量宫颈长度。宫颈长度从宫颈内口测量至外口。采用Bland - Altman图和Wilcoxon符号秩检验评估TA和TV测量值之间的差异。TA测量方法的有效性取决于宫颈长度。虽然TA测量方法平均低估宫颈长度2.0毫米（P < 0.001），但Bland - Altman图显示宫颈越短差异越大。对于经TV扫描测量宫颈长度< 25毫米的女性（n = 30），TA测量值高估宫颈长度12毫米（P < 0.001）。TA检测宫颈长度< 25毫米的敏感度和特异度分别为10%（95%可信区间：2.1 - 26%）和94%（95%可信区间：92 - 96%）；阴性似然比为0.96（95%可信区间：0.84 - 1.08）。当TA测量值截断点为32毫米时（用于检测宫颈长度< 25毫米），ROC曲线下最大面积对应的敏感度为77%，特异度为58%。TA测量不能准确反映TV评估结果，尤其是宫颈较短时。在孕24 - 34周，如果TA测量值< 25毫米就进行TV扫描的策略只能检测出10%的受影响妊娠，且阳性预测值较差，因此作为孕周> 24周出现早产症状和体征的孕妇的预测工具价值有限。孕36周后TA评估宫颈无价值。
