Because (alas!) not all studies are freely made available online, it is not possible to select all available data for our database. This means that there will always be a bias due to the findability of diagnostic data. Paywalls and subscription fees are countless and prohibit an integral look at all data produced.
Another reason is the fact that we treat all used studies as equal. Each individual study is of good quality, but naturally qualities differ. Meta-analyses are prefered over RCT's but their higher lever of proof is not weighed in calculating averages.
Sometimes not all likelihood ratio’s are known, which might falsely imply that for some conditions the likelihood ratio is one. It is possible that the presence of a certain sign does not negatively or positively influence the calculated odds for a certain condition, due to lack of known statistical influencers.
Although only data with good p-values are included, confidence intervals can not be calculated based on the multifarious values from the different studies used. The numbers appearing as answers on your screen certainly have confidence intervals, but we have no way of estimating their size.
What this is and what this is not
This site acts as a tool for calculating odds based on scientific data drawn from research on carefully selected patients. It is therefore impossible to blindly extrapolate calculations made here to individual patients in a doctors office. As a physician you have to rely on a vast range of signs and factors while diagnosing a patient with a disease. Not just some numbers on a screen.
Keep in mind that combining the diagnostic values of several findings is not a sinecure and the level of reliabilty of this tool in no way meets the standards of a meta analysis. All data used and studies consulted are freely recuperated from the internet.
I am not liable for any errors in the content of this website or any decisions taken based on the content of this website, nor for any damage, nuisance or inconvenience resulting from or associated with the use of the content of this website.
None. I made this tool in my spare time and i receive no monetary or other benefits concerning this site. Consider it a gift to you.