Nonparametric Determination of Reference Intervals for Plasma Metanephrine and Normetanephrine

Biochemical diagnosis of phaeochromocytoma using plasma‐free normetanephrine, metanephrine and methoxytyramine: importance of supine sampling under fasting conditions

“…Our findings of increased plasma concentrations of metanephrines during seated compared with supine sampling in patients without PPGL, but lack of increased concentrations in patients with disease, are in agreement with previous studies . The earliest study in this series, which documented lack of influence of upright posture on plasma metanephrines in patients with PPGL, was unfortunately misinterpreted to support use of seated sampling in all patients . As shown here, and also described elsewhere, that interpretation is misguided as it neglects to appreciate that posture associated increases in plasma metanephrines in patients without disease decrease the difference and increase the overlap in concentrations compared to patients with disease.…”

Reference intervals for plasma free metanephrines with an age adjustment for normetanephrine for optimized laboratory testing of phaeochromocytoma

“…This provides some justification for the higher cut-offs used by other laboratories. 11–13,23–25 Nevertheless, as we show here, such higher cut-offs do not appear appropriate for younger patients; an age-adjustment to the cut-offs, as already documented for urinary metanephrines in children, 36,37 provides a solution for measurements of normetanephrine in plasma for both children and adults.…”

“…Upright posture is not only associated with increased plasma concentrations of catecholamines, but also those of their O -methylated metabolites. 19,20,33 It is therefore unsurprising that upper cut-offs for metanephrines determined from blood collected in the seated position 12,23–25 are up to two-fold higher than those determined from samples collected in the supine position. 34…”

“…Despite recommendations to draw blood in the supine position, reference intervals for plasma metanephrines are often established from samples drawn in the seated position. 12,23–25 Consequently, reported upper cut-offs of reference intervals for plasma metanephrines vary widely, for normetanephrine from anywhere between 0.61 and 1.18 nmol/L. 7,8,12,13,23–25…”

Integrating informal learning in college general chemistry courses

“…Interpretation of ordinal responses as continuous, as was applied in this research, may not be suited to all analyses (Sullivan and Artino, 2013). Parametric analysis of ordinal data has been shown to result in erroneous interpretation (Kahler et al, 2008), where non-parametric treatment may be more well-suited (Heider et al, 2004). Interval analysis of typical Likerttype responses, (Strongly agree, agree, neutral, disagree, agree), that may not be suitable to the analysis ordinal responses, may be more strongly justified in this case because it is temporal in nature of the response options rather than indicating an attitude direction and strength of conviction (Albaum, 1997).…”