Page 34 - The diagnostic work-up of women with postmenopausal bleeding

Chapter 2
The three other meta-analyses of TVS reached different conclusions, however.18-20 Tabor et al conducted a meta-analysis of nine studies.18 They included studies only if the corresponding author was able to supply original data. For each included study, the median endometrial thickness per centre was calculated and multiples of the median were used to pool data. They chose not to use a cut-off value, because there were statistically significant differences in endometrial thickness between centres, which may reflect differences in the populations studied or in the method of measuring endometrial thickness by TVS. In this study, a sensitivity of 96% and a specificity of 50% were found.These values give a post-test probability for a negative test of about 1% with a pre-test probability of carcinoma of 10%.These results are comparable to those of Smith-Bindman et al16, but the authors disagreed on the interpretation of the results.The conclusion ofTabor et al was that a 4% false-negative rate is not acceptable and therefore the use of TVS in the evaluation of PMB is not recommended prior to invasive testing.
Gupta et al performed a systematic quantitative review in which they focused on study quality assessment.19 None of the nine studies that used a cut-off for endometrial thickness of 4 mm were of good quality. Only four studies (out of 21) used a 5 mm cut-off, but these employed the best quality criteria. Pooling of the results of these four studies resulted in a LR− of 0.16.This LR implies that a patient with a negative test result (endometrial thickness 5 mm) and pre-test probability of 10% would have a post-test probability of 2.5%. Their conclusion was that TVS can be used to rule out endometrial hyperplasia or carcinoma using an endometrial thickness of 5 mm.
In conclusion, the meta-analyses done by Tabor, Gupta and Smith-Bindman are limited because they are based on previously published data, and probably overestimate the accuracy of predictions based on endometrial thickness. With respect to meta-analysis of randomised trials, individual patient data are considered to be superior to meta-analysis of the literature.26 The use of individual patient data instead of published summary data gives less optimistic but more accurate conclusions. In diagnostic reviews the same might apply. Timmermans et al20 tried to overcome this limitation using a meta-analytic approach in which individual patient data from a series of original studies were combined.This study showed that in previous studies and meta-analyses, the diagnostic accuracy of TVS had been overestimated.Timmermans et al found a lower diagnostic accuracy forTVS than was reported previously: a sensitivity of 95% and a specificity of 47% at a cut-off of 4 mm, giving a post-test probability for a negative test of 1.2%. At a cut-off of 3 mm,
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