Test Outcomes and Additional Examinations for Hemophilia Condition
In the diagnosis of hemophilia, routine laboratory tests play a crucial role. These tests help determine if a person is experiencing heavy or prolonged bleeding, which can affect their hematocrit, hemoglobin, and red blood cell count [1].
The initial tests typically include a prolonged partial thromboplastin time (PTT), a normal prothrombin time (PT), and a platelet count. Additionally, factor VIII and IX assays are conducted to confirm the type and severity of the disorder [2][4].
However, these clotting activity tests have their limitations. To address these, additional tests are employed to provide a more accurate and comprehensive diagnosis.
Clotting Activity Tests vs Additional Tests
| Test Type | Purpose & Description | Difference from Clotting Activity Tests | |-------------------------------|-------------------------------------------------------------------------------------------------------------|------------------------------------------------------------------| | Clotting activity tests | Measure the functional activity of factor VIII (hemophilia A) or factor IX (hemophilia B) in plasma. | Directly quantify clotting factor function; primary diagnostic. | | Mixing studies | Patient plasma mixed with normal plasma to determine if prolonged clotting time corrects. | Distinguish factor deficiency (corrects) from inhibitor presence (does not correct). | | Inhibitor screening | Detect antibodies (inhibitors) that neutralize factor VIII or IX, complicating hemophilia treatment. | Identifies immune-mediated factor inhibitors, not assessed by activity alone. | | von Willebrand factor tests| Measure VWF antigen, activity, and multimer pattern to rule out von Willebrand disease (which can lower factor VIII). | Helps differentiate hemophilia A from von Willebrand disease, which affects factor VIII indirectly. | | Genetic testing | DNA analysis of factor VIII or IX genes to confirm diagnosis, identify carriers, and enable prenatal diagnosis.| Confirms molecular cause beyond functional assays, important for family counseling and prenatal. |
Mixing studies are particularly important as they help distinguish if prolonged PTT is due to a factor deficiency or an inhibitor. Correction upon mixing indicates deficiency; no correction suggests inhibitors [1].
In hemophilia A, because factor VIII can be low in von Willebrand disease (VWD), measurement of VWF antigen and activity is recommended to differentiate, sometimes including multimer analysis [2][3].
Genetic testing is increasingly used for definitive diagnosis, carrier detection (especially in females), and prenatal diagnosis using PCR or cell-free fetal DNA assays [2][4].
These additional tests address limitations of clotting activity assays by identifying inhibitor presence, related disorders mimicking hemophilia, and providing molecular confirmation for better diagnosis and management.
It is essential to note that the main diagnostic lab tests for hemophilia are clotting activity tests, but the additional tests are crucial in providing a complete and accurate diagnosis.
References: [1] National Hemophilia Foundation. (2021). Diagnosis. Retrieved from https://www.hemophilia.org/living-with-hemophilia/treatment/diagnosis [2] National Heart, Lung, and Blood Institute. (2021). Hemophilia. Retrieved from https://www.nhlbi.nih.gov/health-topics/hemophilia [3] World Federation of Hemophilia. (2021). Diagnosis. Retrieved from https://www.wfh.org/publications/files/file/11033/download [4] Centers for Disease Control and Prevention. (2021). Hemophilia. Retrieved from https://www.cdc.gov/ncbddd/hemophilia/hcp/diagnosis.html
