Scientific Lit picture 09

Scientific literature review: Pathology

An assessment of the effect of haemoglobin variants on detection by faecal immunochemical tests
Carroll MR, John C, Mantio D, Djedovic NK, Benton SC. Ann Clin Biochem 2018; doi: 10.1177/0004563218778716 [Epub ahead of print]
BACKGROUND: Faecal immunochemical tests (FIT) for haemoglobin (Hb) are being used in the investigation of colorectal cancer. These tests use antibodies raised to the globin moiety of human Hb. Where the globin structure is abnormal or reduced, it is possible that antibody binding, and thus Hb-detection may be affected.
METHODS: Lysates prepared from whole blood samples of patients with known variants were diluted in manufacturer-specific buffer to 10, 100 and 500 μg Hb/g feces. These samples were analysed on four FIT analysers and the results compared with samples with no known variant present (normal samples).
RESULTS: The results from this study show that of 20 variants tested, three showed a decrease in detection by all four analysers. These were β-thalassemia major and two fetal cord blood samples.
CONCLUSIONS: Of 20 common Hb variants studied, 17 did not affect detection of Hb by the FIT systems tested. Hb variants leading to a reduction in the presence of a globin chain caused a reduction in Hb detection; in such cases, cancers could be missed.
Thirty-three-day storage of dithiothreitol-treated red blood cells used to eliminate daratumumab interference in serological testing
Lorenzen H, Lone Akhtar N, Nielsen M, Svendsen L, Andersen P. Vox Sang 2018; doi: 10.1111/vox.12699 [Epub ahead of print]
BACKGROUND AND OBJECTIVES: Daratumumab binds CD38 on red blood cells causing interference with indirect antiglobulin tests. Dithiothreitol is used to eliminate interference allowing detection of alloantibodies. Hemolysis is observed during storage of dithiothreitol-treated antibody identification panel cells. The objective of this study was to develop a modified method for dithiothreitol treatment to reduce the hemolysis during 33 days of storage and still be able to eliminate daratumumab interference.
MATERIALS AND METHODS: Panel cells were treated with various volumes of 0·2 m dithiothreitol supplied by various manufacturers. Hemolysis Index of dithiothreitol-treated and untreated panel cells was measured and compared on days 1, 15 and 33. Antibody screening tests with dithiothreitol-treated screening cells were performed on samples from 15 daratumumab-treated patients (dose 16 mg/kg) and 34 patients with known alloantibodies. Antibody identifications with dithiothreitol-treated panel cells were performed on seven additional known alloantibodies.
RESULTS: Dithiothreitol treatment with a ratio of 30:25 (red blood cells:dithiothreitol) showed the same degree of hemolysis as with untreated panel cells. Daratumumab interference was eliminated in all 15 samples from daratumumab-treated patients. Twenty-six of 34 alloantibodies were detected, and all seven additional alloantibodies were identified using the modified dithiothreitol treatment. Eight alloantibodies within the Kell system were negative. No decrease in the reaction strength was observed during the 33-day storage period.
CONCLUSION: The modified dithiothreitol method was able to reduce hemolysis during storage and to detect and identify alloantibodies in the presence of daratumumab.
The assessment of iodine status – populations, individuals and limitations
Wainwright P, Cook P. Ann Clin Biochem 2018; doi: 10.1177/0004563218774816 [Epub ahead of print]
Iodine deficiency is a significant global health concern, and the single greatest cause of preventable cognitive impairment. It is also a growing public health concern in the UK particularly among pregnant women. Biomarkers such as urinary iodine concentration have clear utility in epidemiological studies to investigate population-level iodine status, but determination of iodine status in individuals is much more problematic with current assays. This article reviews the available biomarkers of iodine status and their relative utility at the level of both populations and individuals for the investigation of iodine deficiency and iodine excess.
How low can you go? Analytical performance of five automated testosterone immunoassays
La’ulu SL, Kalp KJ, Straseski JA. Clin Biochem 2018; 58: 64–71
BACKGROUND: Testosterone is commonly measured using immunoassays, yet concerns with the accuracy and quality of testing by these methods exist, particularly for low testosterone concentrations. Study objectives were to evaluate selective performance characteristics, including functional sensitivity (FS), of five automated immunoassays for total testosterone.
METHODS: FS, imprecision, assay interference, limit of blank, linearity, and accuracy were assessed using the Abbott ARCHITECT i2000SR, SIEMENS ADVIA Centaur and IMMULITE 2000, Beckman Coulter DxI 800, and Roche MODULAR E170. Comparisons to an in-house liquid chromatography-tandem mass spectrometry (LC-MS/MS) method were performed using patient samples from men, women, boys, and girls.
RESULTS: FS at 20% coefficient of variation (CV) for the ARCHITECT, Centaur, DxI, E170 and IMMULITE assays were 0.14, 1.23, 0.36, 0.77, 3.49 nmol/L, respectively. Total CVs for the 5-day imprecision study were ≤9.0% for all methods. All assays met manufacturer’s claims for hemolysis, icterus, and lipemia interference and limit of blank. Dilution linearity studies had deviations from the target recoveries ranging from 3.4% (ARCHITECT) to 14.3% (DxI). Using National Institute of Standards and Technology Standard Reference Material 971, recoveries ranged from 79.2–149.2% (DxI, male and female, respectively). When compared to LC-MS/MS, more immunoassays under-recovered in men and women and over-recovered in boys and girls. Slopes ranged from 0.71 (IMMULITE, women) to 1.35 (DxI, boys). The combined average for percent bias was higher in boys (28.0%) than men (11.6%), women (22.8%), and girls (25.7%).
CONCLUSIONS: Challenges with accurately measuring testosterone appear to remain for some immunoassays, but not all. While most immunoassays remain optimized for concentrations observed in healthy men, some showed acceptable performance when challenged at lower concentrations.