Trends in clinical laboratory homocysteine testing from 1997 to 2010: the impact of evidence on clinical practice at a single institution.

Background: During the past decade, several clinical trials investigating the potential benefits of homocysteine-lowering therapy for the secondary prevention of vascular events were completed and published. The objective of the study was to determine trends in clinical laboratory testing for homocysteine at a single institution over the time period from 1997 to 2010.
Methods: A single-center, retrospective analysis was performed at a large, academic, tertiary care medical center in the USA. The database was searched for clinical laboratory measurements of plasma or serum homocysteine between January 1, 1997 and December 31, 2010. Individual medical records were reviewed for a subset of 221 unique patients in the 10-year period from 2001 to 2010 who had homocysteine values ≥20 μmol/L.
Results: From 1997 to 2003, there was a 16-fold increase in the annual number of homocysteine assays performed. Testing for homocysteine declined in 2004 and 2006, coinciding with the publication of intervention trials that failed to support a clinical benefit of homocysteine-lowering therapy for the secondary prevention of vascular events. Subgroup analysis suggested that homocysteine testing for the indication of suspected nutritional deficiency or hypercoagulability remained steady despite a decline in testing for the indication of cardiac risk assessment.
Conclusions: The frequency of clinical laboratory testing for plasma or serum homocysteine changed bimodally over the time period from 1997 to 2010. These observations suggest that clinical practice was impacted by emerging evidence from association studies and intervention trials investigating homocysteine as a potentially treatable cardiac risk factor.