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 -20degrees C 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 4degrees C. 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: DeltaC3 (%)=4.14x+1.07 (r=0.9903), and DeltaC4 (%)=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.
Subject(s)
Complement Activation , Complement C3 , Complement C4 , Complement System Proteins , PhlebotomyABSTRACT
Approximately 60-70% of small cell lung carcinoma (SCLC) cases are diagnosed at extensive stage, thus tumor markers for its early detection are needed. Autoantibodies associated with malignancy are present before radiographic detection. Autoantibodies detected using the autoimmune target (AIT) test in patients with some tumors have shown the possibility of autoantibodies to be used as a tumor marker. To overcome the limitations of antinuclear antibody (ANA) test using HEp-2 cell line, the AIT test was developed using human macrophage cell line, IT-1, as a substrate, which showed positive identification of various autoantibodies with a higher level of sensitivity. We report a case of SCLC with autoantibodies against proliferating cell nuclear antigen (PCNA) and centriole in a 70-yr-old man who had a history of heavy alcohol consumption and a 50 pack-yr history of smoking. Results of computed tomography of the chest and abdomen showed a lung mass and multiple metastases. Extensive stage SCLC was confirmed using sputum cytology and lymph node aspiration biopsy. Anti-PCNA (1:1,280) and anti-centriolar (1:320) patterns were detected using the AIT test. Neuron-specific enolase was elevated (38.2 ng/mL). There was no evidence of systemic autoimmune rheumatic disease or chronic hepatitis. This is the first case report in which coexisting autoantibodies against PCNA and centriole associated with SCLC were detected using the AIT test. This case provides some evidence that autoantibodies may be used as a tumor marker for SCLC.