Why is this study important?
The 1997 Olsen et al is one of the most mis-interpreted studies in urogynaecology.
Almost every study reporting the outcomes of the use of mesh for prolapse refer to the Olsen study to confirm a high (29.2%) re-operation rate following natural tissue surgery.
On closer look, the Olsen study had significant shortcomings, likely to have caused a substantial overestimation of the re-operation risk.
How was the study conducted?
A retrospective cohort study of 395 women undergoing natural tissue prolapse surgery in 1995 in Kaiser Permanente Northwest, US.
What were the findings?
The chance of requiring prolapse surgery was reported around 1 in 10 at the age of 80 years old. The re-operation rate was as high as 29.2%.
Most women had significant and relatively high prevalence of factors that increase the risk of prolapse recurrence, such as obesity (35%), smoking (41%) and chronic lung disease (21%).
Moreover, almost a third (31%) of the obese women were morbidly-obese. The study does not report on the proportion of women with chronic constipation, an important risk factor for prolapse recurrence.
The study did not adjust the analysis for the above critical confounding factors among its predominantly high-risk population. The study’s conclusion implied generalisability to other populations.
What were the implications?
The unusually high recurrence rate reported by Olsen in such population should not have come as a surprise. However, the 29.2% failure rate of natural tissue prolapse surgery was widely quoted to support the use of mesh devices to increase the success rate.
Many (uro)gynaecologists generalised the Olsen results and applied them to their own populations, arriving to the conclusion that the overall risk of prolapse recurrence following natural tissue surgery must be as high as 1 in 3. Therefore, the use of a mesh device can be justified to improve the chances of success for women.
An inadvertent mis-interetations of Olsen, and other similar studies, had led to hasty generalisation by surgeons, inaccurate extrapolation by key opinion leaders and opportunistic exploitation by mesh manufacturers.
Subsequently, more robust studies, e.g. Kapoor study 2010 and Morling study 2016, confirmed a re-operation rate of <5% following natural tissue surgery. The largest prolapse trial, Glazener 2017 reported no benefit from the use of mesh over natural tissue surgery.
In April 2019, the FDA ordered the manufacturers of prolapse mesh to remove their devices from the US market.
The way forward?
Referencing the 29.2% failure rate reported by Olsen study to indicate a high risk of re-operation following natural tissue surgery is inaccurate.
Large nation-wide studies are required to confirm the accurate re-operation rates, to determine the modifiable risk factors for recurrence and to compare efficacy of interventions for the small number of women who suffer such recurrence.
As clinicians, we have a duty to maintain up to date knowledge with scientific research by reading the papers ourselves.
Let’s consider the views of key opinion leaders as “processed” i.e. may or may not be a healthy meal for local consumption.
