Serum and Plasma: Introduction, Differences, Keynotes, and Related Footages

Introduction of Serum and Plasma

The serum is a clear yellow fluid that is separated when blood is allowed to clot freely while the plasma is yellowish and slight alkaline fluid, in which blood cells float.

Differences between Serum and Plasma

S. No	Characteristics	Serum	Plasma
1	Clotting factors	Absent	Present
2	Composition	It contains proteins, electrolytes, antibodies, antigens, and hormones.	It contains all suspended blood cells with proteins, salts, lipids, glucose.
3	Water content	90%	92-95%
4	Components	The serum contains proteins like albumin and globulins.	Plasma contains clotting factors and water.
5	Fibrinogen	Absent	Present
6	Cell arrangement	The blood cells are usually attached together by clot formation.	Cells are not attached together and they are suspended in the plasma.
7	Separation Method	Centrifugation after clotting	Centrifugation before clotting
8	Anti-coagulant	Not required	An anticoagulant is required to obtain plasma.
9	Feasibility of Separation	Separation of serum is time-consuming.	The separation of plasma is relatively easy and fast.
10	Volume in blood	Comparatively less	55% of the total volume of blood
11	Density	1.024g/ml	1.025g/ml
12	Storage	The serum can be stored at 2-8 °C for several days.	Frozen plasma can be stored for up to a year at -80 °C.
13	Discoloration	No discoloration on standing	Discoloration on standing
14	Importance	The serum is the primary source of electrolytes.	The plasma helps in the transportation of excretory metabolites and materials in the blood and also in the maintenance of blood pressure and in the regulation of body temperature.
15	Associated terms	Serology: It is the branch of science that deals with the study of serum and analyzing it for diagnostic uses.	Plasmapheresis: It refers to the process of separation of plasma from the blood.
16	Uses	-Clinical diagnostic testing -Animal sera are used as anti-venom, antitoxins, and vaccinations. -It is also used in humans for therapeutic purposes.	Plasma (fresh frozen plasma) is transfused to patients who has coagulation factor defect and warfarin overload. Platelet-rich plasma (PRP) is used if platelet concentrate is not available. The transfusion of plasma is used in patients who suffer from hemophilia, shocks, burns, and other clotting problems.
17	Use of different anticoagulants	No use	1. EDTA-for complete blood cell count (CBC) 2. Fluoride oxalate-Useful in sugar estimation 3. Trisodium citrate: For coagulation study (PT/INR, APTT), ESR test 4. Heparin-Osmotic fragility test, open-heart surgery 5. CPDA-Blood bag ( blood banking)

Keynotes on Serum and Plasma

• Anticoagulant is chemical or agent which prevents the coagulation of blood.
• Blood without anticoagulant on centrifugation gives serum whereas for plasma an anticoagulant is needed.
• Anticoagulants can be used depending on the purpose of the assay.
• The most common anticoagulant applied in laboratory medicine are EDTA, fluoride, trisodium citrate, CPDA, and heparin.
• Ammonium and potassium oxalate anticoagulants are recommended for packed cell volume (PCV), ESR and smear preparation.
• Fluoride oxalate or sodium fluoride is used for blood sugar estimation since it prevents glycosis by interfering with enzyme enolase.
• Ratio of trisodium citrate in coagulation profile test is 1:9 (200 μL citrate+1.8 ml blood) while the ratio such anticoagulant is 1:4 (0.4 ml citrate+ 1.6 ml blood) for ESR test by Westergren Method.
• Anticoagulants for blood banking and transfusion medicine are as follows-

Anticoagulants	Storage time/Shelf-life
Acid-citrate dextrose (ACD)	21 Days
Citrate-phosphate dextrose (CPD)	28 Days
Citrate -phosphate dextrose adenine (CPDA)	35 DAYS
Saline, Adenine, Glucose, and Mannitol (SAGM) solution	42 Days

• For 100 ml blood, a 14 ml anticoagulant is required.

Serum and Plasma Related Footages

Blood collection step

Blood collected in EDTA vial for CBC test

Dispensing blood in clot activator tube for biochemistry and serology tests

Separated serum after clot activator tube centrifugation

The separated plasma of trisodium citrate used blood after centrifugation for clotting panel tests

Citrated plasma for ESR Test

Use of CPDA anticoagulant in blood bag

Stored fresh frozen plasma demonstration

Melted fresh frozen plasma (FFP) ready for transfusion

Platelet Concentrate blood component

Use of heparin anticoagulant for sheep blood collection

Further Readings

1. https://www.differencebetween.com/difference-between-plasma-and-vs-serum/
2. https://www.bioexplorer.net/differences-between-serum-and-plasma.html/
3. Technical Manual of the American Association of Blood Banks-13th Edition, 1999
4. Introduction to Transfusion Medicine –Zarin Bharucha & D.D. Chouhan,1st Edition, 1990
5. Textbook of Medical Laboratory Technology -Praful B. Godkar and Darshan P. Godkar
6. http://medimoon.com/2012/07/difference-between-plasma-and-serum/
7. http://www.microbiologynotes.com/differences-between-serum-and-plasma/
8. https://microbiologyinfo.com/difference-between-serum-and-plasma/
9. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3132215/
10. researchgate.net/publication/23781499_Erythrocyte_storage_in_hypertonic_SAGM_or_isotonic_PAGGSM_conservation_medium_Influence_on_cell_properties