Reduced serum tricyclic levels due to gel separators

Area of Science:

• Clinical Chemistry
• Pharmacology
• Analytical Toxicology

Background:

• Tricyclic antidepressants (TCAs) are crucial for treating various psychiatric conditions.
• Accurate therapeutic drug monitoring (TDM) of TCAs is essential for optimizing efficacy and minimizing toxicity.
• Different blood collection tube types may influence analyte concentrations.

Purpose of the Study:

• To investigate the impact of different blood collection tube types on serum and plasma tricyclic antidepressant concentrations.
• To compare TCA levels obtained using serum separator tubes (SSTs) versus standard serum tubes and heparinized plasma tubes.

Main Methods:

• Sixty-three blood samples were collected from 48 subjects undergoing TCA therapy.
• Samples were simultaneously drawn into Becton-Dickinson Vacutainer tubes: red stopper (serum, no gel), speckled stopper (serum, gel separator), and green stopper (heparinized plasma).
• Concentrations of imipramine, desipramine, amitriptyline, and nortriptyline were measured.

Main Results:

• TCA concentrations were significantly lower in serum collected with gel separator tubes (SSTs) compared to both plasma and serum from red stopper tubes.
• No significant difference was observed between serum from red stopper tubes and plasma.
• This indicates a potential underestimation of TCA levels when using SSTs.

Conclusions:

• Serum separator tubes may lead to falsely low measurements of tricyclic antidepressants.
• Clinicians and laboratories should be aware of this potential bias in TCA TDM.
• Standard serum tubes or plasma tubes are recommended for accurate TCA level determination.