Correct Answer: 4. No additives are required

Serum preparation involves allowing blood to clot naturally, then centrifuging to separate the liquid serum from clot and cells—no anticoagulants needed, unlike plasma.​

Option Analysis

1. Citrate
Sodium citrate chelates calcium to prevent clotting, used for coagulation tests (PT/PTT) yielding plasma. Adding it blocks serum formation by inhibiting clot, so incorrect.

2. Oxalate
Potassium oxalate binds calcium as an anticoagulant for plasma glucose or chemistry tests. Prevents clotting needed for serum separation, making it unsuitable.​

3. EDTA
Chelates calcium/divalent ions for hematology (CBC) preserving cell morphology in plasma. Anticoagulant action stops clot formation essential for serum, so wrong.

4. No additives are required
Plain red-top tubes let blood clot (30-60 min), followed by centrifugation isolates cell-free serum for electrolytes, hormones, enzymes. Correct for clinical serum analysis.

Blood serum preparation additives clinical analysis confirms no anticoagulants needed—plain tubes enable clotting for accurate serum isolation in diagnostics. This blood serum preparation additives clinical analysis guide clarifies options for lab techs, med students, and exam prep.​

Serum vs Plasma Basics

Serum is cell-free fluid post-clotting (no fibrinogen); plasma uses anticoagulants retaining clotting factors. Key for biochemistry panels, hormones—avoid additives to prevent interference.

Additives Comparison Table

No additives ensure reliable serum for 70%+ routine tests without artifact.​

Lab Protocol Steps

1. Collect in plain/red-top tube.

2. Clot 30-60 min at room temp.

3. Centrifuge 10 min at 1000g.

4. Harvest supernatant serum. Store refrigerated. Exam tip: “Serum = clot first; plasma = prevent clot.”