Is a discard tube necessary, when drawing blood for P-Ionized calcium analysis?
Author(s): Novakovic V, Abdija S, Borowik T, Gredal L, Madsen KV, Jacobsen KK
Publication: Clin Biochem, 2019, Vol. 64, Page 64-66
PubMed ID: 30395802 PubMed Review Paper? No
Purpose of Paper
This paper investigated the effects of discarding blood before collection and delayed analysis on the levels of P-ionized calcium in serum.
Conclusion of Paper
P-ionized calcium levels were comparable in specimens from the first (no discard) and second tube in specimens when analyzed ≤96 h although small but significant differences were observed when analyzed after 120 h. However, all except one specimen remained within the 95% limit of agreement, even after 120 h.
Studies
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Study Purpose
The purpose of this study was to investigate the effects of discarding blood before collection and delayed analysis on the levels of P-ionized calcium in serum. Blood from 100 randomly selected outpatients was obtained using a winged collection set with a 19-gauge needle into paired Vacutainer clot activator tubes with gel. Blood was not discarded prior to first collection. Serum was obtained 0.5-2 h after collection by centrifugation at 3580 x g for 4 min and pH adjusted to 7.4. Serum was stored at 4-6˚C for 24, 48, 72, 96, and 120 h before analysis on a Konelab 60i.
Summary of Findings:
P-ionized calcium levels were comparable in specimens from the first and second tube in specimens when analyzed ≤96 h but were 0.0016 mmol/L lower in the second tube than the first tube when analyzed after 120 h (P=0.0068). Even after 120 h the mean difference between the first and second tube remained within the 95% limit of agreement for all specimens except one.
Biospecimens
Preservative Types
- None (Fresh)
Diagnoses:
- Not specified
Platform:
Analyte Technology Platform Electrolyte/Metal Clinical chemistry/auto analyzer Pre-analytical Factors:
Classification Pre-analytical Factor Value(s) Storage Storage duration 24 h
48 h
72 h
96 h
120 h
144 h
Biospecimen Aliquots and Components Aliquot sequential collection 1st collection
2nd collection