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Multicenter Study
. 1998 Jun 6;316(7146):1701-4; discussion 1705.
doi: 10.1136/bmj.316.7146.1701.

Reliability of league tables of in vitro fertilisation clinics: retrospective analysis of live birth rates

E C Marshall  1 , D J Spiegelhalter
Affiliations
Multicenter Study

Reliability of league tables of in vitro fertilisation clinics: retrospective analysis of live birth rates

E C Marshall et al. BMJ. .

Abstract

Objective: To determine to what extent institutions carrying out in vitro fertilisation can reasonably be ranked according to their live birth rates.

Design: Retrospective analysis of prospectively collected data on live birth rate after in vitro fertilisation.

Setting: 52 clinics in the United Kingdom carrying out in vitro fertilisation over the period April 1994 to March 1995.

Main outcome measure: Estimated adjusted live birth rate for each clinic; their rank and its associated uncertainty.

Results: There were substantial and significant differences between the live birth rates of the clinics. There was great uncertainty, however, concerning the true ranks, particularly for the smaller clinics. Only one clinic could be confidently ranked in the bottom quarter according to this measure of performance. Many centres had substantial changes in rank between years, even though their live birth rate did not change significantly.

Conclusions: Even when there are substantial differences between institutions, ranks are extremely unreliable statistical summaries of performance and change in performance, particularly for smaller institutions. Any performance indicator should always be associated with a measure of sampling variability.

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Figures

Figure 1
Figure 1
Estimates and 95% confidence intervals for adjusted live birth rate in each clinic. Estimated adjusted live birth rate for each clinic given in brackets with number of treatment cycles started. Vertical dotted line represents national average of 14%
Figure 2
Figure 2
Median and 95% confidence intervals for rank of each clinic. Estimated adjusted live birth rate for each clinic given in brackets with number of treatment cycles started. Dashed vertical lines divide clinics into quarters according to rank
Figure 3
Figure 3
Estimates and 95% confidence intervals for change in adjusted live birth rate for cycles started between April 1993 and March 1994 compared with those started between April 1994 and March 1995. Observed change in adjusted live birth rate from 1994 to 1995 and accompanying change in rank is shown in brackets
Figure
Figure
Left: distributions showing relative probability of possible true values for success rate of three fictional clinics. Right: distributions showing relative probability of possible true ranks of three clinics—these distributions are obtained empirically by successively sampling from distributions on left and ranking results
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References

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