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HGB Variations During the Day

George, periodically we see patients that have a gram or so difference in their hemoglobin levels which causes some duress with the clinicians.

Recently we had a nursing home patient (s/p hip fracture repair) who had a venous draw early in the morning that was sent to our in house hospital laboratory and resulted in a value of 6.9. The patient was transferred to the hospital where a repeat done in the ED resulted a hemoglobin of 8.2, done around 5 p.m.. The patient was transferred back to the nursing home where a repeat the next day early morning draw resulted in a hemoglobin of 6.9 again. The instruments and patient integrity was checked and everything matched. I have encountered this every now and then over the years and I was wondering if you have any insights. I have found limited old documentation referring to diurnal variation of Hemoglobin values when comparing early morning samples to afternoon to evening sampling. Any assistance that you may be able to give would be greatly appreciated. Thanks. Dr. Bruce King.

Hello, Dr. King, here is a reference from a Scandanavian group that documented diurnal variations of CBC parameters for healthy young men: Sennels HP, Jørgensen HL, Hansen AL, Goetze JP, Fahrenkrug J. Diurnal variation of hematology parameters in healthy young males: the Bispebjerg study of diurnal variations.Scand J Clin Lab Invest. 2011;71:532-41. They document that RBC, HGB, and HCT demonstrate “gradually falling mean levels through the day to nadir around midnight.” The mean HGB variation was 0.29 mmol/L. I admit I can’t make sense of “mmol/L, but fortunately you can get easily find mathematical conversions for anything on the internet. The variation translates in to approximately 0.5 g/d, which doesn’t fully explain the findings for your patient (s). I’m wondering if dehydration could have been part of the picture, also, it may be that if the ER was using a point of care instrument, it may report slightly variant levels. As you collect additional information, please send it along.

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