From the Guidelines
An increase in hemoglobin and platelets does not reliably indicate dehydration, and other diagnostic tools should be used to assess hydration status. According to the ESPEN practical guideline on clinical nutrition and hydration in geriatrics 1, simple signs and tests such as skin turgor, mouth dryness, weight change, urine color or specific gravity should not be used to assess hydration status in older adults.
- Instead, the osmolarity equation (osmolarity = 1.86 (Na+ + K+) + 1.15 glucose + urea + 14) can be used to screen for low-intake dehydration, with an action threshold of >295 mmol/L 1.
- This equation has been found to be useful in predicting serum osmolality in older adults, with a sensitivity of 85% and specificity of 59% 1.
- Directly measured serum osmolality is the most accurate method for assessing hydration status, and older adults and their caregivers should ask healthcare providers for periodic assessment of serum osmolality 1.
- Other causes of elevated hemoglobin and platelets, such as bone marrow disorders, chronic inflammatory conditions, and certain medications, should also be considered and ruled out through further testing and evaluation.
From the Research
Increase in Hemoglobin and Platelets
- An increase in hemoglobin and platelets can be an indicator of various conditions, but it is not a direct indicator of dehydration 2, 3.
- Dehydration can cause an increase in hemoglobin and platelets due to a decrease in plasma volume, but this is not a specific or sensitive indicator of dehydration.
- Other conditions such as polycythemia vera, a myeloproliferative disorder, can also cause an increase in hemoglobin and platelets 3, 4.
- Platelet disorders, such as thrombocytosis, can also cause an increase in platelets, but this is not directly related to dehydration 3.
Hematologic Conditions
- Hematologic conditions, such as thrombocytopenia or thrombocytosis, can cause changes in platelet count, but these conditions are not directly related to dehydration 3.
- A comprehensive history and physical examination are necessary to diagnose hematologic conditions and differentiate them from other conditions that may cause similar symptoms 3.
- The role of platelets in hemostasis, thrombosis, and inflammation is complex and not fully understood, and further research is needed to understand the interrelation of these processes 4.
Laboratory Tests
- Laboratory tests, such as the complete blood count, can provide information on hemoglobin and platelet levels, but these tests must be interpreted in the context of the patient's overall clinical presentation 2.
- The complete blood count is a useful tool for diagnosing and monitoring hematologic disorders, but it is not a specific test for dehydration 2.