검사가 지연된 검체에서 보체 C3, C4 값의 변화
Alterations of Complement C3 and C4 Levels in Delayed Testing
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배경: 채혈 후 C3, C4 농도는 보관조건에 따라 변화한다. 검사가 2시간 이상 지연될 때 검체를 냉동 보관하는 것을 권장하고 있지만, 검사실의 여건상 그대로 시행하기 어렵기 때문에, 저자들은 냉장보관한 검체에서 C3, C4 농도의 변화를 알아보고 초기값을 추정해보고자 하였다. 방법: C3, C4 검사를 10개의 검체에서 시행한 후 검체를 냉장보관하면서 4일간 매일 실시하였다. C3, C4 검사는 비탁법을 원리로 한 자동화기기(Beckman Coulter Inc., USA)를 이용하였다. 결과: 의뢰 당일에 검사한 C3, C4 농도는 86.3±11.8 mg/dL, 21.8±4.6 mg/dL이고, 냉장 보관 후 측정한 농도는 통계적으로 유의한 증가를 보였다(P<0.001, P<0.001). C3 농도는 C3 (mg/dL)=3.55x+87.18 (x=냉장보관한 기간(일), r=0.9909), C4 농도는 C4 (mg/dL)=0.72x+22.3 (r=0.9395)였고, C3 농도의 증가율은 C3 (%)=4.14x+1.07 (r=0.9903), C4 농도의 증가율은 C4 (%)=3.57x+2.48 (r=0.9405)로 나타낼 수 있었다. 결론: 냉장보관한 검체에서 하루마다 C3 농도는 평균 3.55 mg/dL (4.1%), C4 농도는 평균 0.72 mg/dL (3.6%)의 통계적으로 유의한 증가를 보이므로 검사가 지연된 검체에서 측정한 C3, C4 농도는 보정되어야 하며, 본 연구에서 제시한 방법으로 구한 증가량이나 증가율로 역산하여 초기값을 추정할 수 있을 것이다.
Abstract
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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