Minimizing both humidity and temperature in DBS transportation and storage environments is essential to maintaining sample integrity.

Dried blood spots (DBS) have been used in newborn screening (NBS) tests for over 50 years. The Newborn Screening Quality Assurance Program (NSQAP) at the Centers for Disease Control and Prevention (CDC) conducted studies to assess the individual impacts of hematocrit and total-spot volume on characteristics of DBS samples. Per-punch serum volumes decreased 27%, RBC volumes more than doubled, absorption times increased over 300%, and spot diameters decreased marginally between the hematocrits of 40% to 65%. Per-punch serum and RBC volumes decreased logarithmically with lowering total-spot volumes. Patient hematocrit is an uncontrollable variable and inevitably affects the resulting punch from a DBS sample. It may be possible, though, to identify samples that fall outside of an acceptable range by noting certain physical characteristics of the DBS.

The data demonstrated similarities of analyte recovery between the papers, indicating comparability of the devices for newborn screening and other applications.

Background:The clinical significance of the increased concentrations of cardiac troponins observed in patients with end stage renal disease (ESRD) in the absence of an acute coronary syndrome (ACS) is controversial. One proposed explanation is that immunoreactive fragments of cardiac troponin T (cTnT) accumulate in ESRD. We used gel-filtration chromatography (GFC) to ascertain whether fragments of cTnT, which could cross-react in the commercial diagnostic immunoassay (Roche Diagnostics), were the cause of the increased cTnT in the serum of patients with ESRD. Methods: We subjected sera from ESRD patients (n ‫؍‬ 21) receiving dialysis and having increased cTnT concentrations to size-separation GFC. We detected cTnT in the chromatography fractions by use of the same antibodies used in the commercial assay for serum cTnT. Results: In all patients, cTnT immunoreactivity eluted as a major, homogeneous peak in an identical position between the peaks of serum prolactin [relative molecular mass (M r ) 23 000] and albumin (M r 67 000): the elution pattern of cTnT in samples obtained from ACS patients was identical to that of the ESRD patients. There was no evidence that low-molecular-mass (M r <23 000) cTnT fragments were the cause of the increased cTnT in the patients studied. Conclusions: The form of cTnT observed in the serum of patients with kidney failure and immunoreactive in the diagnostic assay is predominantly the free intact form, as in patients with ACS. Our data are consistent