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KMID : 1100820140040030152
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Laboratory Medicine Online
2014 Volume.4 No. 3 p.152 ~ p.156
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Alterations of Complement C3 and C4 Levels in Delayed Testing
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Lee Z-Young
Jearn La-He
Park Ile-Kyu
Kim Think-You
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Abstract
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Background: In vitro levels of complement C3 and C4 proteins are sensitive to storage conditions. To avoid in vitro complement activation when testing is delayed, serum should be frozen at -20℃ within 2 hr of venipuncture. However, this is impractical in routine laboratory work. Therefore, we investigated alterations in C3 and C4 levels in refrigerated specimens over time and derived formulae to estimate initial levels of complement concentrations in delayed testing.
Methods: Ten fresh specimens were measured for C3 and C4 concentrations and were refrigerated at 4℃. We measured C3 and C4 levels in refrigerated samples daily for 4 days using an automated nephelometer (Beckman Coulter Inc., USA).
Results: C3 and C4 levels were significantly increased over time in refrigerated specimens (P<0.001, P<0.001, respectively). The increments in C3 and C4 levels were described by the equations: C3 (mg/dL)=3.55x+87.18 (r=0.9909), and C4 (mg/dL)=0.72x+22.3 (r=0.9395), where x=the number of days samples were refrigerated before testing. Increases in C3 and C4 concentrations were described on a percentage basis by the equations: ΔC3 (%)=4.14x+1.07 (r=0.9903), and ΔC4 (%)=3.57x+2.48 (r=0.9405).
Conclusions: As the measured C3 and C4 concentrations increased by 3.55 mg/dL (4.1%) and 0.72 mg/dL (3.6%) per day in refrigerated specimens, the levels of C3 and C4 should be adjusted in delayed testing. We proposed that the formulae presented be used to back-calculate initial levels of C3 and C4 concentrations.
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KEYWORD
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Complement C3, Complement C4, Delayed testing
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