Optimized procedures for testing plasma metanephrines in patients on hemodialysis

Diagnosis of pheochromocytomas and paragangliomas in patients receiving hemodialysis is troublesome. The aim of the study was to establish optimal conditions for blood sampling for mass spectrometric measurements of normetanephrine, metanephrine and 3-methoxytyramine in patients on hemodialysis and specific reference intervals for plasma metanephrines under the most optimal sampling conditions. Blood was sampled before and near the end of dialysis, including different sampling sites in 170 patients on hemodialysis. Plasma normetanephrine concentrations were lower (P < 0.0001) and metanephrine concentrations higher (P < 0.0001) in shunt than in venous blood, with no differences for 3-methoxytyramine. Normetanephrine, metanephrine and 3-methoxytyramine concentrations in shunt and venous blood were lower (P < 0.0001) near the end than before hemodialysis. Upper cut-offs for normetanephrine were 34% lower when the blood was drawn from the shunt and near the end of hemodialysis compared to blood drawn before hemodialysis. This study establishes optimal sampling conditions using blood from the dialysis shunt near the end of hemodialysis with optimal reference intervals for plasma metanephrines for the diagnosis of pheochromocytomas/paragangliomas among patients on hemodialysis.

The Pitfalls of Using Research Grade Immunoassays for Thyroid Health Measurements

Introduction: Immunoassay technology is subject to matrix interferences that can produce inaccurate results and incorrect conclusions when using samples not previously validated. While many commercially available research grade (RG) immunoassay kits are available, caution should be applied when using RG kits for thyroid health assessments, particularly on samples from pregnant individuals whose blood chemistry is unique to non-pregnant individuals. Question: Do RG immunoassay kits reliably provide precise and accurate measurements of thyroid health biomarkers in serum Standard Reference Materials (SRMs) from pregnant and non-pregnant donors? Methods: T4, T3, rT3, Tg and TSH measurements were conducted on SRMs 971, Hormones in Frozen Human Serum, and SRM 1949, Frozen Prenatal Serum, using RG immunoassay kits. When available, performance was assessed against validated FDA approved immunoassays or mass spectrometric (MS) methods. Results: RG kits were variable, inaccurate, or imprecise for four of the six biomarkers assessed. RG kit total thyroid hormone measurements overall performed comparably to MS methods, except rT3 measurements, which were twofold greater than mass spectrometric measurements (971M RG mean = 0.51 ng/mL, MS mean = 0.20 ng/mL, p &lt; 0.0001; 971F RG = 0.48 ng/mL, MS = 0.18 ng/mL, p &lt; 0.0001) and had CVs over 30 %. RG kit Tg measurements varied sometimes by as much as tenfold (971M means of 6.50 ng/mL up to 63.3 ng/mL, p &lt; 0.0001; 971F means of 0.350 ng/mL up to 14.5 mg/mL, p &lt; 0.0001). TSH values differed by RG kit manufacturer (971M means of 1.27 µIU/mL up to 1.82 µIU/mL, p &lt; 0.0001; 971F means of 1.36 µIU/mL up to 2.27 µIU/mL, p &lt; 0.0001) and by dilution scheme using the same manufacturer with one case indicating a diagnosis of hypothyroid versus normal TSH levels (1949 non-pregnant undiluted mean = 2325 pg/mL, half dilution mean = 1631 pg/mL, p &lt; 0.0001). Conclusions: RG immunoassays are often used for research projects because they do not require expensive equipment and are simple to conducted. However, we demonstrate here that not all kits are accurate for all patient samples. By utilizing a matrix matched SRM with well-defined quantities of thyroid health biomarkers, one can assess method accuracy, making measurements from different methods comparable. Thereby, data can be harmonized to contribute reliable data on thyroid biomarkers to advance the field of thyroid health.

Optimized procedures for diagnostic testing for pheochromocytoma and paraganglioma in patients on hemodialysis

Background Diagnosis of pheochromocytomas and paragangliomas in patients receiving hemodialysis is troublesome. Aim To establish optimal conditions for blood sampling for mass spectrometric measurements of normetanephrine, metanephrine and 3-methoxytyramine in patients on hemodialysis and specific reference intervals for plasma metanephrines under the most optimal sampling conditions. Methods Blood was sampled before and near the end of dialysis, including different sampling sites in 170 patients on hemodialysis. Results Plasma normetanephrine concentrations were lower (P < 0.0001) and metanephrine concentrations higher (P < 0.0001) in shunt than in venous blood, with no differences for 3-methyxytyramine. Normetanephrine, metanephrine and 3-methoxytyramine concentrations in shunt and venous blood were lower (P < 0.0001) near the end than before hemodialysis. Upper cut-offs for normetanephrine were 34% lower when the blood was drawn from the shunt and near the end of hemodialysis compared to blood drawn before hemodialysis. Conclusion This study establishes optimal sampling conditions using blood from the dialysis shunt near the end of hemodialysis with optimal reference intervals for plasma metanephrines for the diagnosis of pheochromocytomas/paragangliomas among patients on hemodialysis.

Spectral reflectivity variations of Brassica napus depending on degree of soil moisture

&lt;p&gt;Studying of the optical properties of agricultural vegetation is one of the methods for plants condition estimation, prediction of their development and changes influenced by natural and anthropogenic factors.&lt;/p&gt;&lt;p&gt;The work is dedicated to the investigation of spectral reflectance function of agricultural &lt;em&gt;Brassica napus&lt;/em&gt; taking into account the degree of soil moisture. When most of the agricultural lands in Belarus are covered with vegetation in summer, employing the optical properties of agricultural vegetation for deciphering the soil depends on the degree of soil moisture. Insufficient numbers of days in year when the soil is not covered by vegetation or is in a plowed state requires in-situ optical measurements, because there are more than 50 % cloudy conditions in the year, especially in spring and autumn time.&lt;/p&gt;&lt;p&gt;The study has been carried out near the Minsk 11.06.2020 (53.837004&amp;#186; N, 27.487597&amp;#186; E) in clear, cloudless day. The relief for investigated field is hilly-ridge, characterized by a predominance of elevation marks from 250 to 300 m and it is actively sown field. During the spectrometric measurements, the field has been sown with &lt;em&gt;Brassica napus&lt;/em&gt; in the phenological phase of pod formation.&lt;/p&gt;&lt;p&gt;When studying the spectral reflectance of &lt;em&gt;Brassica napus&lt;/em&gt;, in-situ spectrometric measurements and analysis of a multispectral image have been carried out. Spectrometric measurements have been carried out by FSR-02 spectrometer (spectral range 400-900 nm, spectral resolution 4.3 nm) aiming to retrieve spectral reflectance function.&lt;/p&gt;&lt;p&gt;The normalized vegetation index NDVI has been used for analyzing the multispectral image from Landsat 8 OLI system with a spatial resolution of 30 m. The results of a study of the correlation between the reflection coefficient of &lt;em&gt;Brassica napus&lt;/em&gt;&lt;span&gt;&amp;#160;and the area of observed soils will be presented. In addition, the results of the analysis of quasi-synchronous values of the NDVI index and in-situ measurements of the spectral reflectance of &lt;em&gt;Brassica napus&lt;/em&gt; will be discussed.&lt;/span&gt;&lt;/p&gt;