Learning from pitfalls and pearls 

Different ways to describe pitfalls and pearls 

Pitfalls and Pearls

Tips and Traps 

Masquerades and mimics 

Red flags and alarm features

Bias and error 

Logical fallacies 

Clinical clangers and caveats

Notes

Caveat: a warning or proviso of specific stipulations, conditions, or limitations. 

Clanger: something that you say by accident that embarrasses or upsets someone

Pitfalls in the interpretation of common biochemical tests 

1. Ruth M Ayling

Abstract

This review considers some of the more common problems in the interpretation of the results of biochemical tests and, where possible, highlights ways in which errors can be identified or avoided.

http://dx.doi.org/10.1136/pmj.76.893.129

Reference ranges

The reference range is the interval into which the central 95% of apparently healthy people fall. 

If the distribution is Gaussian this is the range two standard deviations above and below the mean. 

With non-Gaussian distributions the range is obtained by deleting 2.5% at the upper and lower ends of ranked values. 

In other words, one in 20 (ie, 5%) apparently healthy people will have a value outside this range. 

The finding of a value outside the quoted reference range does not therefore necessarily indicate the presence of a pathological cause and the more tests performed which are independent variables, the greater the probability of finding a result outside the reference range. 

Similarly, the presence of disease is not excluded by a result within the reference range