Exclusion table.

Background
Anaemia is highly prevalent and commonly caused by nutritional deficiencies. Guidelines often include an algorithm to find the underlying cause. Here, we compared diagnostic algorithms and suggested laboratory tests for anaemia in clinical practice guidelines in countries with similar healthcare systems, focusing on iron, vitamin B12 and folate deficiency in the general adult population.
Methods
We searched for diagnostic guidelines on anaemia in the Trip, Guidelines International Network and country specific databases. To be selected, the guidelines had to include diagnostic criteria or algorithms to determine the cause of anaemia in the general adult population.
Results
In total, 14 records were included. For iron deficiency anaemia, guidelines varied in diagnostic criteria ranging from use of ferritin only, to ferritin in various combinations with a variety of other parameters, with different cut-off values. For vitamin B12 or folate deficiency, besides measurement of vitamin B12 or folate, some guidelines mentioned methylmalonic acid or homocysteine. Quality of evidence underlying cut-offs and parameters was variable, and laboratory aspects were underrepresented.
Conclusions
There was a lot of variation in the included diagnostic algorithms, especially for iron deficiency anaemia. Differences in cut-off values were seen, even when using similar diagnostic strategies. Furthermore, supporting evidence was variable. Further research is needed to determine optimal algorithms. Our findings highlight the need for inclusion of relevant laboratory aspects in guidelines, appropriate diagnostics and clinical decision limits.