Evaluation of blood microsampling techniques and sampling sites for the analysis of drugs by HPLC-MS.

Background: the potential for whole blood sampling (20 µl) in toxicokinetic studies to reduce the sample volume was investigated. Blood microsamples were collected in three ways, either as a dried blood spot (DBS), a blood sample collected in a micropipette placed in a plastic tube and mixed with water or as plasma in the normal manner.

Results: blood samples on the DBS and the whole blood microtube (WBMT) were compared along with DBS and plasma to determine the toxicokinetic data equivalency. The DBS and WBMT comparison was shown to be equivalent, as demonstrated on a correlation plot with an R(2) value of 0.97 for an x = y plot. The plasma comparison with DBS also gave a good correlation. A correction factor (x(2)) was applied to the blood data to allow for the distribution of the compound between plasma and bloods, and therefore, a direct comparison could be made. The correlation plot derived from the sample data gave an R(2) value 0.98 (x = y plot), indicating dataset equivalency. Sampling sites were evaluated in a dog study. Blood was collected from the peripheral region, in this case the ear, and a venous region of the dog; and spotted onto DBS cards. Comparison of the mean area under the curve data for the sampling sites showed equivalent data: 5095 and 5175 ng.h/ml for the 25 mg/kg dose and 16695 ng.h/ml and 16000 ng.h/ml for the 50 mg/kg dose for the ear and the venous samples, respectively.

Conclusion: the DBS cards were shown to be an equivalent microsampling process when compared with WBMT and conventional plasma analysis. With the added benefits of sample storage, shipment and ease of use for DBS, this technology could change the way samples are taken and then analyzed in bioanalysis in the future.