Transcript Slide 1

UOG Journal Club: March 2012
Agreement between two- and three-dimensional transperineal ultrasound
methods in assessing fetal head descent in the first stage of labor
E. A. Torkildsen, K. Å. Salvesen and T. M. Eggebø
Volume 39, Issue 3, Date: March 2012, pages 310–315
Journal Club slides prepared by Dr Aly Youssef
(UOG Editor for Trainees)
Background
Transperineal ultrasound (TPU) can assess fetal head descent before
and during labor
The literature is sparse on this subject, and there is no agreement
regarding the superiority of 3D versus 2D ultrasound to assess fetal
head descent
Although 2D and 3D transperineal ultrasound in the labor ward are
reproducible and repeatable techniques, the intermethod agreement
between 2D and 3D techniques has not been investigated
Agreement between two- and three-dimensional transperineal ultrasound
methods in assessing fetal head descent in the first stage of labor
Torkildsen et al., UOG 2012
Objective: to study intraobserver repeatability and
intermethod agreement between 2D and 3D ultrasound in
assessing fetal head descent during the first stage of labor
Agreement between two- and three-dimensional transperineal ultrasound
methods in assessing fetal head descent in the first stage of labor
Torkildsen et al., UOG 2012
Two transperineal ultrasound (TPU) parameters
were assessed in the study
Head–perineum distance
(Eggebø UOG 2006)
• The shortest distance between the outer limit of
the fetal skull and the perineum
• Assessed in a transverse view
Angle of progression
(Barbera UOG 2009)
• The angle between the pubic symphysis
and a line tangential to the fetal skull
• Assessed in a mid-sagittal view
Agreement between two- and three-dimensional transperineal ultrasound
methods in assessing fetal head descent in the first stage of labor
Torkildsen et al., UOG 2012
Patients and Methods
•
•
106 primiparous women with a live singleton term fetus in cephalic presentation and a
diagnosis of prolonged first stage were included in the study
Women were examined in the lithotomy position, with empty bladder, after rupture of
membranes and between contractions
For each woman both the “angle of progression” and “fetal head–perineum
distance” were assessed using two different methods of acquisition
2D
(3 acquisitions)
•
3D
(one volume acquired and analyzed later 3
times for each parameter)
All volumes and images were obtained and stored by one operator without measured values,
and all 2D and 3D measurements were later performed by another operator blinded to clinical
assessment and labor outcome
Agreement between two- and three-dimensional transperineal ultrasound
methods in assessing fetal head descent in the first stage of labor
Torkildsen et al., UOG 2012
Statistical analysis
Intraobserver repeatability
Was expressed as:
1. the difference between the highest and
lowest measurements
2. the intraclass correlation coefficient
(ICC)
3. the repeatability coefficient (the range
within which two measurements by the
same observer will fall for 95% of
subjects)
Intermethod agreement (2D–3D)
Was performed using:
1. the mean of 3 measurements for each
technique
2. Intermethod agreement was expressed using
the two-way random effects ICC
3. Cohen’s kappa was used to assess agreement
for categorical data
In addition, linear regression analysis was performed to investigate the
association between angle of progression and fetal head–perineum distance
(expressed using the Pearson correlation coefficient – “r”)
Agreement between two- and three-dimensional transperineal ultrasound
methods in assessing fetal head descent in the first stage of labor
Torkildsen et al., UOG 2012
Results: Intraobserver repeatability
Fetal head–perineum distance
2D
3D
Mean measurement (mm)
40.1
39.3
Repeatability coefficient
(mm)
± 4.1
± 1.7
ICC (95% CI)
0.94 (0.92–0.96)
0.99 (0.99–1.00)
Angle of Progression
2D
3D
Mean measurement (º)
108.7
111.0
Repeatability coefficient (º)
± 6.7
± 5.7
ICC (95% CI)
0.91 (0.87–0.93)
0.94 (0.91–0.96)
ICC, intraclass correlation coefficient
Agreement between two- and three-dimensional transperineal ultrasound
methods in assessing fetal head descent in the first stage of labor
Torkildsen et al., UOG 2012
Results: Intermethod agreement
Fetal head–perineum distance
Angle of progression
ICC (95% CI)
0.95 (0.93–0.97)
0.93 (0.89–0.95)
Intermethod 95% limits
of agreement
-5.8 to +7.2 mm
-8.9º to 13.7º
Mean 2D–3D difference
0.7 mm
2.4º
Cohen’s kappa (95% CI)
0.85 *
(0.75-0.95)
0.79 †
(0.68-0.91)
ICC, intraclass correlation coefficient
* Using 40 mm as a cut-off level
† Using 110º as a cut-off level
Agreement between two- and three-dimensional transperineal ultrasound
methods in assessing fetal head descent in the first stage of labor
Torkildsen et al., UOG 2012
Results: Bland–Altman plots of intermethod
agreement between 2D and 3D measurements
There was a significant, albeit small,
mean difference over the range of
the measured values for both fetal
head–perineum distance and angle
of progression.
angle of progression
Agreement between two- and three-dimensional transperineal ultrasound
methods in assessing fetal head descent in the first stage of labor
Torkildsen et al., UOG 2012
Results: Association between angle of progression
and fetal head–perineum distance
2D: r=−0.72
The association was significant
at the 0.01 level for both the 2D
(r=0.72) and 3D (r=0.71) scan
methods
r = Pearson correlation coefficient
Agreement between two- and three-dimensional transperineal ultrasound
methods in assessing fetal head descent in the first stage of labor
Torkildsen et al., UOG 2012
Discussion
• Both intraobserver repeatability and intermethod agreement between
2D and 3D acquisitions were good
• The results suggest that 2D and 3D ultrasound might be used
interchangeably in fetal head descent assessment in labor
• The intraobserver repeatability was slightly better in 3D than 2D
acquisitions
• The association between angle of progression and fetal head–
perineum distance was good for both 2D and 3D ultrasound
Agreement between two- and three-dimensional transperineal ultrasound
methods in assessing fetal head descent in the first stage of labor
Torkildsen et al., UOG 2012
Strength of the study
•
Inclusion of a large, homogeneous and well-defined population
Weakness
•
Variation in 2D measurements was analyzed using three different acquisitions,
while for 3D measurements the same acquired volume was uploaded three
times
•
Possible bias due to the performance of the 3D invariably after the 2D
evaluation which might have been the reason of wider angle (mean difference
2.4º) and shorter distance (mean difference, 0.7 mm) in 3D measurements
observed in the study. However, the differences were small and probably lacking
clinical importance
Agreement between two- and three-dimensional transperineal ultrasound
methods in assessing fetal head descent in the first stage of labor
Torkildsen et al., UOG 2012
Conclusion
• The intraobserver repeatability and agreement between 2D and 3D
ultrasound assessment of fetal head descent in labor is good
• 2D and 3D ultrasound methods might be used interchangeably
• These results may not be applicable to the second stage of labor where
further studies are necessary