Is paleness always reliable? Unfortunately NO !!
- Patient’s natural skin pigment
– Cyanosis can mask the paleness
- Diameter of subepidermal vessels
– Vasoconstriction from cold may cause pallor without anemia
– Vasodilation due to inflammation can cause redness
The best location to look for anemia
- Conjunctival rim
– Conjunctival rim pallor if present has a +LR of 16.7. If examination of anterior rim of inferior conjunctiva reveals the same pale fleshy colour as the posterior aspect of conjunctiva, it is present. Normally, anterior rim has bright red colour.
- Conjunctival pallor also has good +LR = 4.7
- The next best location to find pallor is palm
– palmar crease pallor has +LR of 7.9
– palmar pallor has +LR of 5.6
Nail bed pallor has no diagnostic value
NO physical sign argues against diagnosis of anemia.
- Most have -LR of >0.4, conjunctival and palmar pallor have -LR of 0,6 and 0.4 respectively.
- This means presence of pallor is good for dx of anemia, but absence of it does not exclude anemia.
- Conjunctiva and palm are the 2 best locations to find anemia in a dark skinned patient.
- Diagnosis of anemia could not be excluded just by physical examination alone. It could be present but not obvious. NO PHSICAL SIGN argues against the diagnosis of anemia.
Reference: Evidence-based physical diagnosis, Steven McGee – 2nd ed