BACKGROUND: Dried blood spot (DBS) sampling is a blood collection tool that uses a finger prick to obtain a blood drop on a dried blood spot card. It can be used for therapeutic drug monitoring, a method that uses blood drug concentrations to optimize individual treatment. DBS sampling is thought to be a simpler way of blood collection compared to venous sampling. The aim of this study was to evaluate the quality of dried blood spots from tuberculosis patients all around the world based on quality indicators in a structured assessment procedure.
METHODS: Total 464 DBS cards were obtained from four countries: Bangladesh, Belarus, Indonesia and Paraguay. The quality of the DBS cards was assessed using a checklist consisting of 19 questions divided into four categories: the integrity of the DBS materials, appropriate drying time, blood volume and blood spot collection.
RESULTS: After examination, 859 of 1856 (46 %) blood spots did not comply with present quality criteria. In 625 cases (34%), this was due to incorrect blood spot collection. The DBS cards from Bangladesh, Indonesia and Paraguay seemed to be affected by air humidity, causing the blood spots not to dry appropriately.
CONCLUSION: New tools to help obtain blood spots of sufficient quality are necessary as well as environmental specific recommendations in order to determine plasma-concentrations correctly. Additionally, 3% of the DBS cards were rejected because the integrity of the materials suggesting that the quality of plastic zip lock bags currently used to protect the DBS cards against contamination and humidity may not be sufficient.