Variability of Nt-proANP and C-ANP.
BACKGROUND
Natriuretic peptides are frequently measured in patients with chronic cardiac failure (CCF). We set out to compare the variability of atrial natriuretic peptide (C-ANP) and its precursor N-terminal pro-ANP (Nt-proANP) to decide which would be more suitable for routine use.


METHODS
Ten males with compensated CCF (age range 62-76 years) were studied, with matched controls. Blood was withdrawn every 2 min for 90 min from a forearm vein, and plasma C-ANP and Nt-proANP were measured by radioimmunoassay.


RESULTS
Levels were elevated in the patient group [C-ANP: median 268 (range 171-423) vs. 40 (28-56) ng L-1, P < 0.0002 Mann-Whitney U-test; Nt-proANP: 1955 (562-4451) vs. 621 (409-961) pmol L-1, P < 0.003]. A similar number of 'peaks' was observed in both groups with both peptides, about one every 10 min, and their relative height was similar in both groups. Variability was greater for C-ANP than for Nt-proANP in both patients [coefficient of variation of means 51 (range 36-70) vs. 3.6 (2.1-6.2)%, P < 0.01; sign test] and controls [65 (49-83) vs. 8.9 (4.7-13.5)%, P < 0.01].


CONCLUSIONS
Nt-proANP is less variable than C-ANP and hence more suited for diagnostic or prognostic use.
Royal Victoria Hospital, Belfast, Queen's University of Belfast, UK.
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G
McDowell
C
C
Patterson
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Maguire
C
C
Shaw
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DP
Nicholls
C
C
Hall
D000368:Aged; D009320:Atrial Natriuretic Factor / Q000097:blood*; D015415:Biomarkers / Q000097:blood; D016022:Case-Control Studies; D006333:Heart Failure / Q000097:blood* / Q000188:drug therapy; D006801:Humans; D008297:Male; D008875:Middle Aged; D010446:Peptide Fragments / Q000097:blood; D011498:Protein Precursors / Q000097:blood*; D011863:Radioimmunoassay / Q000379:methods; D018709:Statistics, Nonparametric
D015415:Biomarkers; D010446:Peptide Fragments; D011498:Protein Precursors; D009320:Atrial Natriuretic Factor