Following an analysis of individual patient data (IPD), doctors were able to offer a less painful surgery to treat the most common type of hernia.

When people age, muscles become weaker and the intestines can sometimes push through weak spots causing a hernia. These can be painful and in some cases require surgery to treat. Doctors can either perform open or laparoscopic surgery. Laparoscopic surgery involves making a few small cuts to allow special instruments to be used. Over 40 clinical trials have compared the benefits and risks of the two surgeries but most have been too small to give definitive results.

The EU Hernia Trialists Collaboration was formed in 1998 to review the evidence and determine which surgery had better outcomes for patients. They obtained IPD from 25 trials involving 4165 patients. After analysing these data, they found that patients who had laparoscopic surgery reported less pain after surgery than those who had open surgery, contradicting an earlier review that had found the opposite.

The team reached a different conclusion because they were able to include more data in their review. Data on pain was measured in nearly all of the trials but it was only reported in three of the published articles. By seeking out IPD, the study authors were able to draw a clearer picture of the evidence.

This post is part of a series on the value of sharing individual patient data.


McCormack K, Grant A, Scott N. Value of updating a systematic review in surgery using individual patient data. Br J Surg 2004;91:495-9. Abstract