Table 4

Correlation of phenylalanine and tyrosine concentrations and phenylalanine: tyrosine concentration ratio between different types of samples
Real time Delay 1 h Delay 2 h
Variable r p r p r p
Correlation between serum and dried blood
Phe .50 .01
Tyr .96 < .001
[Phe]/[Tyr] .96 < .001
Correlation between serum and microdialysate
Phe -.11 .64 -.15 .48 -.24 .25
Tyr .54 .01 .23 .28 .04 .84
[Phe]/[Tyr] .76 < .001 .52 .01 .28 .18

Phe = phenylalanine; Tyr = tyrosine; [Phe]/[Tyr] = phenylalanine: tyrosine concentration ratio.

The correlation analysis of phenylalanine and tyrosine concentrations and of the phenylalanine: tyrosine concentration ratio ([Phe]/[Tyr]) between microdialysis fluid and serum was performed with samples taken simultaneously (“Real time”) and with microdialysate samples taken one hour (“Delay 1 h”) and two hours (“Delay 2 h”) after blood sampling. To assess the above-mentioned correlations Pearson’s correlation coefficients (r) were calculated for each patient, then transformed to Fisher-Z values (Fisher r-to-Z transformation) and averaged. Resulting mean Fisher-Z values were retransformed to r values (reversed Fisher transformation).

Grünert et al.

Grünert et al. Nutrition Journal 2013 12:60   doi:10.1186/1475-2891-12-60

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