Prenasal thickness to nasal bone length ratio: effectiveness as a second or third trimester marker for Down syndrome

OBJECTIVE

To assess the value of the prenasal thickness to nasal bone length ratio (PT/NBL) for detecting trisomy 21 (T21) after the first trimester.

METHOD

Two examiners blinded to fetal T21 status retrospectively measured prenasal thickness (PT) and nasal bone length (NBL) of T21 and control fetuses at 15-36 weeks' gestational age on two-dimensional images from all T21-screening ultrasounds from November 2010 to April 2013. ROC curve analysis and its diagnostic values determined the best cut-off value for the ratio. Interobserver reproducibility was assessed.

RESULTS

Good quality ultrasound profile images were available for 26 fetuses with T21 compared to 91 normal fetuses. The median PT/NBL ratio was 1.28 for T21 and 0.73 for control fetuses (p<0.0001). The PT/NBL ratio performed significantly better (AUC 0.99; 95%CI 0.97-1) than either PT (0.82; 0.73-0.91) or NBL (0.91; 0.85-0.98). The optimal PT/NBL ratio cut-off was 0.98, with a sensitivity of 88.5% [76.2-100%] and a specificity of 100%. Interobserver variability was low.

CONCLUSION

The PT/NBL ratio is a strong marker for detecting T21 in the second and third trimesters, significantly more effective than either indicator alone.

[Role of endocervical curettage in the screening for cervical cancer: apropos of a series of 31 cases]

We present a study of 31 cases of pathologic cervical smear with an inconclusive colposcopy. The aim of this study was to compare the results of the cervical smear, colposcopy, cervical biopsy, endocervical curettage and conization. The endocervical curettage is a valuable complement to the colposcopy, especially in the case of an inconclusive colposcopy.