Artificially raised creatinine concentrations due to analytical interference for samples contaminated with total parenteral nutrition fluid.

Background: A sample received in the laboratory from a patient receiving total parenteral nutrition (TPN) indicated that the patient may have renal dysfunction, but the results were not considered to be reliable enough to report. Investigations using a reference method for measurement of creatinine confirmed positive interference in the creatinine assay and distribution of samples via an External Quality Assessment (EQA) Scheme showed that this positive interference was method dependent.

Methods: Residual TPN fluid (Nutriflex Lipid Special) left in the bag after the patient had completed the infusion was collected and added to a patient serum pool in increasing amounts and distributed to different laboratories for analysis of creatinine and glucose through an EQA Scheme.

Use of Dried Blood Spot Specimens to Monitor Patients with Inherited Metabolic Disorders.

Monitoring of patients with inherited metabolic disorders (IMDs) using dried blood spot (DBS) specimens has been routinely used since the inception of newborn screening (NBS) for phenylketonuria in the 1960s. The introduction of flow injection analysis tandem mass spectrometry (FIA-MS/MS) in the 1990s facilitated the expansion of NBS for IMDs. This has led to increased identification of patients who require biochemical monitoring.

Effect of blood volume on analytical bias in dried blood spots prepared for newborn screening external quality assurance.

Dried blood spots (DBS) are used for the analysis of more than 2000 biomarkers. We assessed a range of analyte concentrations and diameters of DBS. DBS samples were created by the application of increasing volumes of whole blood prepared by the UK NEQAS Quality Assurance Laboratory.

Newborn screening for sickle cell disorders using tandem mass spectrometry: three years' experience of using a protocol to detect only the disease states.

Background Tandem mass spectrometry (MS/MS) has recently become an alternative method for the newborn screening of sickle cell disorders (SCD), as it is able to detect haemoglobin (Hb) peptides following digestion of bloodspots with trypsin. Using the SpOtOn Diagnostics Reagent Kit, we previously developed a screening protocol to detect only the disease states of SCD, using action values based on the ratio between the variant Hb peptide to wild-type peptide abundances for the HbS, C, D, O, E and Lepore peptides. Methods Action values using the ratios between the wild type HbA (ßT1-3) peptides and the foetal Hb (γT2) peptide were developed to identify bloodspot samples from premature and transfused infants.

Effect of Dried Blood Spot Quality on Newborn Screening Analyte Concentrations and Recommendations for Minimum Acceptance Criteria for Sample Analysis.

Background: The analysis of dried blood spots has been used routinely for newborn screening since the early 1970s, and the number of disorders screened has expanded substantially in recent years. However, there is a lack of evidence regarding minimum blood spot quality acceptance criteria for sample analysis.

Methods: Blood pools were spiked with phenylalanine, tyrosine, leucine, methionine, octanoylcarnitine, decanoylcarnitine, isovalerylcarnitine, glutarylcarnitine, thyroid-stimulating hormone, and immunoreactive trypsinogen to concentrations at the analytical cutoffs used in UK screening protocols.

The use of trypsin to confirm the presence of macrocreatine kinase on isoenzyme electrophoresis.

Background: Macrocreatine kinase (MCK) type 1 is a high molecular weight form of CK that is non-pathological. Identification of MCK is beneficial in preventing unnecessary investigations that may follow a persistently elevated CK of unknown origin. Currently, gel filtration chromatography can be used as a confirmatory technique, but it is laborious, time-consuming and expensive.