Time-lapse algorithms and morphological selection of day-5 embryos for transfer: a preclinical validation study

The agreement between the algorithms in selecting the best day-5 embryo for transfer was highly variable, raising concerns as to their applicability in different clinical settings.

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Volume 109, Issue 2, Pages 276–283.e3


Ashleigh Storr, Pg.D., Christos Venetis, Ph.D., Simon Cooke, Ph.D., Suha Kilani, Ph.D., William Ledger, Ph.D.



To determine the agreement between published time-lapse algorithms in selecting the best day-5 embryo for transfer, as well as the agreement between these algorithms and embryologists.


Prospective study.


Private in vitro fertilization center.


Four hundred and twenty-eight embryos from 100 cycles cultured in the EmbryoScope.



Main Outcome Measure(s)

Interalgorithm agreement as assessed by the Fleiss kappa coefficient.


Of seven published algorithms analyzed in this study, only one of the 18 possible pairs showed very good agreement (κ = 0.867); one pair showed good agreement (κ = 0.725), four pairs showed fair agreement (κ = 0.226–0.334), and the remaining 12 pairs showed poor agreement (κ = 0.008–0.149). Even in the best-case scenario, the majority of algorithms showed poor to moderate kappa scores (κ = 0.337–0.722) for the assessment of agreement between the embryo(s) selected as “best” by the algorithms and the embryo that was chosen by the majority (>5) of embryologists, as well as with the embryo that was actually selected in the laboratory on the day of transfer (κ = 0.315–0.802).


The results of this study raise concerns as to whether the tested algorithms are applicable in different clinical settings, emphasizing the need for proper external validation before clinical use.

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Fertility and Sterility

Editorial Office, American Society for Reproductive Medicine

Fertility and Sterility® is an international journal for obstetricians, gynecologists, reproductive endocrinologists, urologists, basic scientists and others who treat and investigate problems of infertility and human reproductive disorders.