Data Interpretation:
Miscellaneous Tests
Question 1
You are provided with the prothrombin time results using two different thromboplastins on a number of patients on oral anticoagulants as well as several normal healthy individuals.
One thromboplastin is the WHO rabbit reference material and the other is an in-house rabbit material you have prepared in your laboratory.
Plasma Sample |
PT (s) WHO Reference Thromboplastin |
PT (s) In-House Thromboplastin |
| 1 | 32 | 15.5 |
| 2 | 46 | 16 |
| 3 | 50 | 19.5 |
| 4 | 46 | 16 |
| 5 | 15 | 12 |
| 6 | 43 | 16 |
| 7 | 13 | 12 |
| 8 | 45 | 18.5 |
| 9 | 32 | 15.5 |
| 10 | 13 | 11 |
| 11 | 55 | 18 |
| 12 | 48 | 17 |
| 13 | 13 | 11 |
| 14 | 14 | 12 |
| 15 | 55 | 18 |
| 16 | 55 | 20 |
| 17 | 29 | 15 |
A. What is the ISI of this home made material?
B. Would you use this thromboplastin in your laboratory? If not, why not?
Question 2
From the data shown in the attached graph derive the ISI (roughly) for thromboplastin. If you click HERE you can open the graph in a new window.
The WHO Reference thromboplastin has an ISI of 1.0. Points A, B and C are designed to help you.
Question 3
A 20 year old woman is 32/40 weeks pregnant. She attends the antenatal clinic for a routine check up. You are asked to see her because of the following results:
| Hb | 10.1g/dlL |
| WCC | 6.2 x 109/L |
| Platelets | 80 x 109/L |
| MPV | 10.1 fL |
1) What would you do immediately and what investigations would you request?
2) What are the possible diagnoses?
Question 3
A 23-year-old man is investigated for a possible bleeding disorder whilst living in Paris. He has a bleeding time performed and this is found to be significantly prolonged at 26 minutes (NR: <10 minutes).
a. Briefly outline the principles of the bleeding time
b. What abnormalities would explain the prolonged bleeding time?
c. What additional tests would you request?
d. Is this test still commonly performed?
Question 4
Briefly explain the principles of the Activated Clotting Time and the Thrombin Time
1. What factors can affect the ACT or the thrombin time?
2. Why don’t we use the thrombin time to monitor patients on cardio-pulmonary bypass?
Question 5
A 64-year-old man undergoes an aortic valve replacement. Prior to coming off bypass he is given protamine sulphate to reverse the UFH and suddenly his BP falls he becomes profoundly hypotensive.
1. What is protamine sulphate and how does it work?
2. What do you think might have happened?
Question 6
A 56-year-old man with a long history of COPD is admitted for surgery.
His pre-operative investigations show a Hb of 19g/dL and an Hct of 0.58
His pre-operative clotting screen shows:
| Test | Patient | Reference Range |
| PT | 20s | 11-14s |
| APTT | 47s | 23-35s |
Click HERE for the Answers!
Try to resist the temptation to look at the answers before you work through all the questions!