Timing of human preimplantation embryonic development is confounded by embryo origin.
To what extent do patient- and treatment-related factors explain the variation in morphokinetic parameters proposed as embryo viability markers?
Up to 31% of the observed variation in timing of embryo development can be explained by embryo origin, but no single factor elicits a systematic influence.
Several studies report that culture conditions, patient characteristics and treatment influence timing of embryo development, which have promoted the perception that each clinic must develop individual models. Most of the studies have, however, treated embryos from one patient as independent observations, and only very few studies that evaluate the influence from patient- and treatment-related factors on timing of development or time-lapse parameters as predictors of viability have controlled for confounding, which implies a high risk of overestimating the statistical significance of potential correlations.
Infertile patients were prospectively recruited to a cohort study at a hospital fertility clinic from February 2011 to May 2013. Patients aged <38 years without endometriosis were eligible if ≥8 oocytes were retrieved. Patients were included only once. All embryos were monitored for 6 days in a time-lapse incubator.
A total of 1507 embryos from 243 patients were included. The influence of fertilization method, BMI, maternal age, FSH dose and number of previous cycles on timing of t2-t5, duration of the 2- and 3-cell stage, and development of a blastocoel (tEB) and full blastocoel (tFB) was tested in multivariate, multilevel linear regression analysis. Predictive parameters for live birth were tested in a logistic regression analysis for 223 single transferred blastocysts, where time-lapse parameters were investigated along with patient and embryo characteristics.
Moderate intra-class correlation coefficients (0.16-0.31) were observed for all parameters except duration of the 3-cell stage, which demonstrates that embryos from one patient elicit clustering at a patient level. No single patient- and treatment-related factor was found to systematically influence the timing from cleavage to blastocyst stage, which indicates that no individual patient-related factor can be identified that separately explains the clustering throughout the entire developmental stages. The blastocyst parameters were more affected by patient-related factors than cleavage stage parameters, as tEB occurred significantly later with older age (0.29 h/year (95% confidence interval: CI 0.03; 0.56)), while both tEB and tFB occurred significantly later with increasing dose of FSH (tEB: 0.12 h/100 IU FSH (95% CI 0.01;0.24); tFB 0.14 h/100 IU FSH (95% CI 0.03;0.27)) and with more previous attempts (tEB: 1.2 h/attempt (95% CI 0.01;2.5); tFB 1.4 h/attempt (0.10;2.7)). Fertilization method affected timing of the first division, with ICSI embryos cleaving significantly faster than IVF embryos (-3.6% (95% CI -6.4; -0.77)), whereas no difference was found in the subsequent divisions. The univariable regression analysis identified female age, cumulative FSH dose, degree of blastocyst expansion, score of the inner cell mass and timing of full blastocyst formation as predictors of live birth. The timing of full blastocyst formation (tFB) did not remain significant when adjusting for age, number of previous cycles and cumulative FSH dose, which were the parameters shown to influence tFB in the mixed regression model.
Only good prognosis patients were enrolled, so these results may not be generalized to all infertile women. Not all patient-related factors were investigated.
Our findings underline the importance of treating embryos as dependent observations and suggest a high risk of patient-based confounding in retrospective studies. The impact of confounders and the embryo origin needs to be addressed in order to apply appropriate statistical models in observational studies. Furthermore, this observation emphasizes the need for RCTs for evaluating use of time-lapse parameters for embryo selection.
Funding for the cohort study was provided by the Lippert Foundation, the Toyota Foundation, the Aase og Einar Danielsen foundation and NordicInfu Care research grant. Research at the Fertility Clinic, Aarhus University Hospital is supported by an unrestricted grant from MSD and Ferring. K.K. is funded by a grant from the Danish Council for Independent Research Medical Sciences. The authors declare no competing interest.
Kirkegaard K
,Sundvall L
,Erlandsen M
,Hindkjær JJ
,Knudsen UB
,Ingerslev HJ
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Prospective study of automated versus manual annotation of early time-lapse markers in the human preimplantation embryo.
How does automated time-lapse annotation (Eeva™) compare to manual annotation of the same video images performed by embryologists certified in measuring durations of the 2-cell (P2; time to the 3-cell minus time to the 2-cell, or t3-t2) and 3-cell (P3; time to 4-cell minus time to the 3-cell, or t4-t3) stages?
Manual annotation was superior to the automated annotation provided by Eeva™ version 2.2, because manual annotation assigned a rating to a higher proportion of embryos and yielded a greater sensitivity for blastocyst prediction than automated annotation.
While use of the Eeva™ test has been shown to improve an embryologist's ability to predict blastocyst formation compared to Day 3 morphology alone, the accuracy of the automated image analysis employed by the Eeva™ system has never been compared to manual annotation of the same time-lapse markers by a trained embryologist.
We conducted a prospective cohort study of embryos (n = 1477) cultured in the Eeva™ system (n = 8 microscopes) at our institution from August 2014 to February 2016.
Embryos were assigned a blastocyst prediction rating of High (H), Medium (M), Low (L), or Not Rated (NR) by Eeva™ version 2.2 according to P2 and P3. An embryologist from a team of 10, then manually annotated each embryo and if the automated and manual ratings differed, a second embryologist independently annotated the embryo. If both embryologists disagreed with the automated Eeva™ rating, then the rating was classified as discordant. If the second embryologist agreed with the automated Eeva™ score, the rating was not considered discordant. Spearman's correlation (ρ), weighted kappa statistics and the intra-class correlation (ICC) coefficients with 95% confidence intervals (CI) between Eeva™ and manual annotation were calculated, as were the proportions of discordant embryos, and the sensitivity, specificity, positive predictive value (PPV) and NPV of each method for blastocyst prediction.
The distribution of H, M and L ratings differed by annotation method (P < 0.0001). The correlation between Eeva™ and manual annotation was higher for P2 (ρ = 0.75; ICC = 0.82; 95% CI 0.82-0.83) than for P3 (ρ = 0.39; ICC = 0.20; 95% CI 0.16-0.26). Eeva™ was more likely than an embryologist to rate an embryo as NR (11.1% vs. 3.0%, P < 0.0001). Discordance occurred in 30.0% (443/1477) of all embryos and was not associated with factors such as Day 3 cell number, fragmentation, symmetry or presence of abnormal cleavage. Rather, discordance was associated with direct cleavage (P2 ≤ 5 h) and short P3 (≤0.25 h), and also factors intrinsic to the Eeva™ system, such as the automated rating (proportion of discordant embryos by rating: H: 9.3%; M: 18.1%; L: 41.3%; NR: 31.4%; P < 0.0001), microwell location (peripheral: 31.2%; central: 23.8%; P = 0.02) and Eeva™ microscope (n = 8; range 22.9-42.6%; P < 0.0001). Manual annotation upgraded 82.6% of all discordant embryos from a lower to a higher rating, and improved the sensitivity for predicting blastocyst formation.
One team of embryologists performed the manual annotations; however, the study staff was trained and certified by the company sponsor. Only two time-lapse markers were evaluated, so the results are not generalizable to other parameters; likewise, the results are not generalizable to future versions of Eeva™ or other automated image analysis systems.
Based on the proportion of discordance and the improved performance of manual annotation, clinics using the Eeva™ system should consider manual annotation of P2 and P3 to confirm the automated ratings generated by Eeva™.
These data were acquired in a study funded by Progyny, Inc. There are no competing interests.
N/A.
Kaser DJ
,Farland LV
,Missmer SA
,Racowsky C
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