A comparative evaluation of lithium estimation for samples collected in different tubes and its stability on storage

Abstract

PURPOSE:Lithium (Li) is a well-established drug for the treatment of bipolar affective disorders. Li as a drug is known to possess a narrow therapeutic index. Thus, regular monitoring of blood Li in patients receiving Li therapy is essential. Plain tubes with clot activator are known to interfere with Li estimation. The current study was planned to compare Li estimation in sera from vacutainers with clot activator, and plasma from sodium heparinized vacutainers with that of Li estimation in sera from glass vials. The time-dependant stability of Li estimation on storage at 2°C–8°C for 48 h in these three set of tubes was also evaluated.MATERIALS AND METHODS:Blood from the patients on Li therapy (n = 100) was collected in 3 different collection tubes: plain vacutainer with clot activator (S), Sodium heparinized vacutainer (P) and Glass vial (G) and was analyzed by ion selective electrode (ISE) analyzer for Li levels. Secondary aliquots were also taken from each type of collection tube and stored at 2°C–8°C. Time-dependant stability of Li estimation was checked at 12 h, 24 h, and 48 h. ANOVA followed by Tukey's posttest was performed to calculate statistical significance taking glass vial as reference collection tube. Bland–Altman plots were plotted to compare between three collection tubes at baseline. Stability on storage was defined when >95% of the samples were within allowable error limit for that time point taking baseline levels as reference.RESULTS:A mean bias of 0.18 mmol/L and mean percentage bias of 19.9% in Li levels was observed between serum from (S) than serum from (G). This difference was found to be statistically significant. However, statistically nonsignificant mean bias of 0.02 mmol/L and mean percentage bias of 3.34% in Li levels was observed between plasma from (P) and serum from (G). Time-dependant stability was observed more in glass vials as compared to vacutainers with clot activator or sodium heparin.CONCLUSION:Serum from glass vial should be the preferred method for blood collection to determine Li levels.

Comparative Evaluation of Serum Lithium Estimation Using Plain Glass Vial and Serum Clot Activator Vacutainer by Reflectance Photometry

“…13 Ikkurthi et al in their study have concluded that plain vacutainers with clot activators show higher bias and statistically significant higher levels of Li than glass vacutainers. 14 Thus, the study further validates the previous study by Sampson et al 7 in which it was shown that silicone present as an additives in the clot activators vacutainer interacts with the membrane of Li ISE membrane. This interaction results in a false elevation of Li values when estimated on the ISE analyzers.…”

Comparative evaluation of serum lithium estimation in serum samples using plain glass vial and serum clot activator vacutainer by reflectance photometry principle

“…Ikkurthi S et al in their study have concluded that plain vacutainers with clot activators show higher bias and statistically significant higher levels of Li than glass vacutainers[13]. Thus, the study further validates the previous study by Sampson et al .,1997.…”

“…[11] In comparison to common laboratories, serum lithium is estimated mainly by ion selective electrode methods which work mainly on the principle of generation potential difference between the electrodes. [12] Ikkurthi S et al in their study have concluded that plain vacutainers with clot activators show higher bias and statistically significant higher levels of Li than glass vacutainers [13]. Thus, the study further validates the previous study by Sampson et al,1997.…”