Question

4. Solve this mixing study case study using this reference information given below. Identify the missing coag factor(s).
AGED SERUM(AS): Rich in Factors VII, IX, X, XI, XII. Deficient in II, V, VIII.
ABSORBED PLASMA(AP): Rich in factors V, VIII, XI,XII. Deficient in II, VII, IX, X (vitamin K dependent factors)
(Both AS & AP have XI, XII, neither has II.)
Reference ranges: PT 11.0 -14.0 seconds   PTT 25.0 – 36.0 seconds (Note: You will need to know the reference ranges for the Lab final exam!)
Case study patient: PT = 20 seconds       PTT = 80 seconds

Mixing studies with aged serum and adsorbed plasma:

Aged serum mixed with patient plasma 1:1                                          PT = 14.0 seconds      PTT = 33 sec

Mixing studies with Absorbed plasma with patient plasma 1:1        PT = 20.0 seconds      PTT = 84 sec

Which factor is missing?

Answer 1

Answer : Factors VII, IX and X

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Mixing studies are performed to determine if the prolonged APTT / PT is due to deficiency of one of the clotting factors or there is an inhibitor in the patients serum against one of the clotting factors.

If the APTT / PT becomes normal, after mixing study it means that the patient's serum lacked some clotting factor which was now supplied by the normal serum so that blood clots.

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Patient: PT = 20 seconds       PTT = 80 seconds

After mixing studies with aged serum and patient plasma 1:1 ,  PT = 14.0 sec ; PTT = 33 sec

Here, after mixing with aged serum, the PT and APTT became normal. So, the aged serum contains the deficient clotting factors which now supplimented the patients serum. Aged serum is rich in Factors VII, IX, X, XI, XII. So, the deficient factor is one among these.

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Patient: PT = 20 seconds       PTT = 80 seconds

After mixing studies with absorbed plasma with patient plasma 1:1 ,  PT = 20.0 sec PTT = 84 sec

Here, even after mixing with absorbed plasma, the PT and APTT are prolonged. Absorbed plasma is rich in factors V, VIII, XI,XII. This means that these are not the deficient factors.

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So, combining both the mixing studies, certain factors in the aged serum which is not present in the absorbed serum corrected the factor deficiencies. They are : Factors VII, IX and X.