Validity and reliability of a portable handheld dynamometer compared to a fixed isokinetic dynamometer to assess forearm torque strength.

To evaluate the effect of treatment on forearm rotation, torque muscle strength can be assessed using an isokinetic device (IKD) or a wrist dynamometer (WD). The aims of this study were 1) to determine concurrent validity and intra- and inter-rater reliability using the WD, and to examine correlations between WD and IKD in different positions; and 2) subsequently, to establish the intermethod reproducibility between WD as a handheld (HHD) or fixed device. We conducted a cross-sectional study in which torque strength was measured in healthy participants by two observers using an IKD and a WD. Study endpoints were concurrent validity (Pearson's r), intra- and inter-rater reliability, intermethod reproducibility (intraclass correlation coefficient: ICC) and measurement error (limits of agreement: LoA). Concurrent validity ranged, in the 2 studies assessing it, from r 0.37 to 0.52 for pronation and from r 0.50 to 0.82 for supination, with wide 95% confidence intervals. ICC for intra-rater reliability for pronation ranged from 0.85 to 0.91 and for supination from 0.91 to 0.95. ICC for inter-rater reliability for pronation ranged from 0.84 to 0.96 and for supination from 0.92 to 0.96. Despite the excellent intra- and inter-rater reliability and intermethod reproducibility for the WD-HHD and fixed WD, validity was low when compared to IKD and wide LoA indicated a high measurement error of approximately 20%. These results suggest that the WD cannot replace the IKD isometric mode for pronation and supination. LEVEL OF EVIDENCE: 2.

Sulfhydryl compounds influence immunoreactivity, structure and functional aspects of lipoprotein(a).

Human plasma Lp(a) is susceptible to various sulfhydryl compounds. In this study we present evidence indicating that after treatment of Lp(a) with sulfhydryl compounds, immunoreactivity is changed, structural changes occur and functional characteristics regarding the numerous kringle structures in apo(a) disappear. Purified Lp(a) was subjected to variable concentrations (0.01-10 mM) of various sulfhydryl compounds: DTT, 2-mercapto-ethanol (BME), N-acetylcysteine (NAC) and homocysteine (HCys). Free SH groups were blocked by iodoacetamide. Reduced and alkylated Lp(a) was tested in two ELISAs, one detecting apo(a) alone and one detecting apo(a)-apoB complexes. In both ELISAs polyclonal antibodies were used. For comparison a commercial apo(a) IRMA utilizing two monoclonal antibodies was used. The results indicate that a similar decrease in response of both ELISAs is observed, whereas the IRMA response is less affected. Western blotting of "DTT treated" Lp(a) after SDS-PAGE under nonreducing conditions showed that separate apo(a) and apoB-100 bands became detectable at 1 mM DTT. Native PAGE (2.5-16%) indicated structural changes of Lp(a) beginning to occur at 0.03 mM DTT. Epsilon-aminocaproic acid-inhibitable binding of "DTT-treated" Lp(a) to Desafib-X decreased with increasing DTT concentrations in concert with a loss of the capacity of Lp(a) to inhibit plasminogen activation upon treatment with DTT. The observed immunological and functional changes of Lp(a) indicate that apo(a) kringle function is severely affected by sulfhydryl compounds.