From the Guidelines
For a petechiae workup, start with a complete blood count (CBC) and coagulation studies (PT, PTT, INR), and consider additional labs such as peripheral blood smear, liver function tests, renal function tests, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP) to assess for thrombocytopenia, coagulation disorders, or other underlying conditions. When evaluating for Antiphospholipid Syndrome (APS), it is recommended to include lupus anticoagulant, anticardiolipin antibodies, and anti-β2 glycoprotein I antibodies in the diagnostic workup 1. The most recent guidance from the ISTH-SSC subcommittee on lupus anticoagulant/antiphospholipid antibodies suggests concurrent testing for LA, aCL IgG and IgM, and aβ2GPI IgG and IgM, and measurement of LA in citrated plasma according to the ISTH-SSC recommendations 1. Some key points to consider in the interpretation of antiphospholipid antibodies include:
- The use of enzyme-linked immunosorbent assays (ELISAs) for the measurement of aCL and aβ2GPI, with moderate and high titer thresholds set at 40 Unit (U) and 80 U levels, respectively 1
- The importance of correlating lab results with clinical findings and patient history, and considering further specialized testing or hematology consultation if initial tests are inconclusive and petechiae persist
- The role of IgM and IgA isotypes in APS diagnosis, with IgG isotype considered more clinically relevant than IgM 1
- The need to differentiate between classification criteria and assessment of aPL in clinical care, with classification criteria being strict and meant for participant inclusion in studies and trials, and laboratory detection for APS diagnosis in daily practice being broader and meant to diagnose each APS patient to optimize their management 1.
From the Research
Workup for Petechiae
The workup for petechiae includes a range of laboratory tests and evaluations to determine the underlying cause of the condition. Some of the key tests and evaluations that may be included in the workup are:
- Complete blood count (CBC) to evaluate for anemia, thrombocytopenia, or other blood cell abnormalities 2, 3
- Coagulation tests, such as prothrombin time (PT) and partial thromboplastin time (PTT), to evaluate for coagulopathy 2, 3
- Inflammatory tests, such as C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR), to evaluate for inflammation or infection 3
- Blood cultures to evaluate for bacteremia or sepsis 3, 4
- Monospot test to evaluate for infectious mononucleosis 3
- Nasopharyngeal rapid tests to evaluate for respiratory viruses 3
- Cerebrospinal fluid culture to evaluate for meningitis or other central nervous system infections 3
Evaluation for Antiphospholipid Syndrome (APS)
There is no direct evidence in the provided studies regarding the evaluation for Antiphospholipid Syndrome (APS) in patients with petechiae. However, it is known that APS can cause petechiae and other skin manifestations, and evaluation for APS may be considered in patients with unexplained petechiae or other symptoms suggestive of the condition.
Other Considerations
Other considerations in the workup for petechiae include:
- Physical examination to evaluate for signs of infection, inflammation, or other underlying conditions 2, 3, 4
- Medical history to evaluate for underlying medical conditions that may be contributing to the petechiae 2, 3, 4
- Family history to evaluate for genetic disorders that may be contributing to the petechiae 5
- Diagnostic tests, such as echocardiography, to evaluate for cardiac abnormalities that may be contributing to the petechiae 4