Clinician-Ordered Peripheral Smear Review by a Pathologist Has Low Clinical Utility-A Reference Laboratory Perspective.

Background: Clinician-ordered peripheral smear review by pathologist (CPSR) is commonly ordered and has been recommended for decades. However, the clinical utility of this labor-intensive test in the reference laboratory has not been examined. The objective of this study is to assess hematologic abnormalities identified in CPSR orders and to correlate them with complete blood count (CBC) and laboratory-derived smear review (LDSR) in the reference laboratory.

Small volume retinol binding protein measurement by liquid chromatography-tandem mass spectrometry.

Background: The measurement of plasma concentrations of retinol binding protein is a component of nutritional assessment in neonatal intensive care. However, serial testing in newborns is hampered by the limited amount of blood that can be sampled. Limitations are most severe with preterm infants, for whom close monitoring may be most important.

Laboratory Utilization and Analytical Validation of Fecal Electrolyte Tests.

Background: Chronic diarrhea can be categorized as fatty, watery, or inflammatory. Watery diarrhea is further divided into secretory or osmotic types and can be differentiated by measuring fecal electrolytes and osmotic gap. However, with widespread use of endoscopy, it is unclear if these measurements are being used clinically.

Establishing evidence-based thresholds and laboratory practices to reduce inappropriate treatment of pseudohyperkalemia.

Background: Unrecognized pseudohyperkalemia (PHK), defined as an artificial increase in measured potassium concentration, due to thrombocytosis and leukocytosis can lead to inappropriate patient treatment. Understanding the laboratory and patient characteristics that increase risk of PHK is key to preventing diagnostic errors.

Methods: Serum/plasma potassium results collected at 2 laboratories over 4years were selected based on blood cell counts collected within 24h and whole blood potassium concentrations determined within 2h of the serum/plasma sample.

Endogenous alkaline phosphatase interference in cardiac troponin I and other sensitive chemiluminescence immunoassays that use alkaline phosphatase activity for signal amplification.

Background: False positive cardiac troponin results can lead to inappropriate diagnosis. Our laboratory workflow includes systematic quality practices to identify false positive cardiac troponin I (cTnI) results reported by the DxI AccuTnI+3 assay, which uses alkaline phosphatase (ALP) for signal amplification. Recently, a sample with elevated cTnI failed our quality standards and was found to have extremely elevated endogenous ALP activity.

Factors influencing naproxen metabolite interference in total bilirubin assays.

Background: The factors influencing naproxen metabolite O-desmethylnaproxen (ODMN) positive interference in diazo-based Jendrassik and Grof (JG) total bilirubin (Tbil) assays and lack of interference in direct bilirubin (Dbil) assays have not been resolved. The objective of this study was to understand the conditions causing this interference pattern.

Methods: Pooled normal and ultra-filtered plasma samples spiked with ODMN and naproxen were measured on the Beckman Coulter DxC and AU instruments.

Therapeutic concentrations of hydroxocobalamin interferes with several spectrophotometric assays on the Beckman Coulter DxC and AU680 chemistry analyzers.

Background: High doses of hydroxocobalamin (OHCob) are used to treat cyanide poisoning and cardiac complications. Since OHCob absorbs at multiple wavelengths often used in colorimetric assays, spurious laboratory results are likely to occur. The objective of this study was to examine interference caused by OHCob in colorimetric assays measured using the Beckman Coulter DxC and AU680.

Determination of the kinetics and thermodynamics of ligand binding to a specific inactive conformation in protein kinases.

Recent interest in inactive kinase conformations has generated the need to develop new biochemical tools to study them. Here, we describe the use of a fluorescent probe that selectively and potently binds to a specific inactive conformation of protein kinases. This allows for the thermodynamics and kinetics of ligand binding to be determined.

Affinity purification of protein kinases that adopt a specific inactive conformation.

Several protein kinases have been characterized in a specific inactive form called the DFG-out conformation. Unlike the active conformation which is conserved in all kinases, the inactive DFG-out conformation appears to be accessible to only certain kinases. This inactive conformation has been successfully targeted with highly selective kinase inhibitors, including the cancer drugs imatinib and sorafenib.

Affinity reagents that target a specific inactive form of protein kinases.

A number of small-molecule inhibitors have been developed that target the catalytic domains of protein kinases that are not in an active conformation. An inactive form that has been observed in several kinases is the DFG-out conformation. This conformation is characterized by an almost 180 degrees rotation of the conserved Asp-Phe-Gly (DFG) motif in the ATP-binding cleft relative to the active form.

Equally potent inhibition of c-Src and Abl by compounds that recognize inactive kinase conformations.

Imatinib is an inhibitor of the Abl tyrosine kinase domain that is effective in the treatment of chronic myelogenic leukemia. Although imatinib binds tightly to the Abl kinase domain, its affinity for the closely related kinase domain of c-Src is at least 2,000-fold lower. Imatinib recognition requires a specific inactive conformation of the kinase domain, in which a conserved Asp-Phe-Gly (DFG) motif is flipped with respect to the active conformation.

Reactive landing of gas-phase ions as a tool for the fabrication of metal oxide surfaces for in situ phosphopeptide enrichment.

Zirconium, titanium, and hafnium oxide-coated stainless steel surfaces are fabricated by reactive landing of gas-phase ions produced by electrospray ionization of group IVB metal alkoxides. The surfaces are used for in situ enrichment of phosphopeptides before analysis by matrix-assisted laser desorption ionization (MALDI) mass spectrometry. To evaluate this method we characterized ZrO(2) (zirconia) surfaces by (1) comparison with the other group IVB metal oxides of TiO(2) (titania) and HfO(2) (hafnia), (2) morphological characterization by SEM image analysis, and (3) dependence of phosphopeptide enrichment on the metal oxide layer thickness.