Letter to the editor: Pre-operative evaluation of peritoneal deposits using multidetector computed tomography in ovarian cancer. Some considerations

The Editor,

We read with interest the article by Chandrashekhara et al entitled “Pre-operative evaluation of peritoneal deposits using multidetector computed tomography in ovarian cancer“[1]. First we want to congratulate the authors for the in-depth analysis in relation to diagnostic tests (CT) used for the evaluation of patients with peritoneal carcinomatosis from ovarian origin before citoreductive surgery. The article evaluates the role of multidetector CT (MDCT) in identifying peritoneal deposits pre-operatively. However, we would like to make some comments on the results related to the evaluation of diagnostic tests in the published study.

We believe that in addition to calculating sensitivity, specificity and predictive values, the coefficients of positive and negative probability (CPP and CPN, respectively) should have been calculated as well. This is because the sensitivity and specificity values, despite completely defining validity (the degree to which a test measures what it is supposed to measure) for the diagnostic test, have the disadvantage of not providing relevant information when it comes to making a clinical decision when faced with a certain test result. The CPP and CPN express a unified summary of sensitivity and specificity, and therefore do not depend on the disease prevalence in each location and permit comparison between different studies, unlike predictive values, which are only valid for the location at which they were calculated [2,3]. In addition, the authors believe that the point estimate of parameters (not including 95%) is valid. This is not entirely correct, since all specific determinations are subject to random error, whose magnitude depends on the sample size and dispersion of individual observations.

When we refer to diagnostic test studies, parameters ≥80% are considered to be optimum or high. As we can see, these are optimal only for sensitivity for peritoneal implants or peritoneal thickening in the evaluation of two areas (umbilical and hypogastric region, the latter being at the limit of what may be considered optimum). The reported specificity is acceptable. We can not use the diagnostic test to confirm the presence of peritoneal disease with peritoneal thickening (positive predictive value), although there is a tendency to exclude the presence of disease (negative predictive value) with the information provided, within the margin of error. Based on data from the study, we could not recalculate the data with confidence intervals of 95%, which would be useful to contrast the presence of the null value (that percentage would be 50%) in some of them. This would be interesting for a correct analysis of the data. Nor can we calculate in this way the CPP and CPN, which in turn allow us to compare similar studies.

To conclude, we must be careful and methodical with all details involved in a research study in order to contribute efficiently to its comprehensibility and usefulness to the researchers and clinicians for whom it is intended.

Yours etc.,