Chiefs’ Inquiry Corner – 10/2/2019

October 7, 2019

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The hemoglobin assay measures hemoglobin protein in whole blood, while the hematocrit measures the volume of red cells in whole blood. At Bellevue Hospital and most laboratories, the hematocrit is a calculated value, based on the red cell number and the mean cell volume, and is subject to inaccuracy. In a 1981 study of over 13,000 children, anemia was not detected by hematocrit levels in 20-50% of children who would be diagnosed with anemia based on low hemoglobin levels. It is postulated that surgeons may reach for hematocrit more often because most point-of-care blood gas machines offer real-time hematocrit values while in the operating room. 

The diagnostic performance of CA-125 for the diagnosis of epithelial ovarian cancer is highly dependent on a patient’s menopausal status. In pre-menopausal women in particular, the specificity is very limited as there are many other conditions that cause mild elevations in CA-125, including menstruation, endometrioma, and pregnancy. However, when high cutoff values of CA-125 are used (>200 U/mL), and when only post-menopausal women are considered, the positive predictive value rises to 70%, and the negative predictive value is 85%. Despite the decent performance of the assay in this population, biomarkers should guide but not dictate the decision to refer for diagnostic laparotomy. 

References: CA-125 and Ovarian Masses  
The Centers for Disease Control and Prevention estimate that more than 30% of people will experience an episode of herpes zoster in their lifetime and approximately 20% of these cases will recur. One study randomized 100 patients age >50 years old with a history of herpes zoster to receive the live attenuated herpes zoster vaccine or placebo and found that antibodies against varicella zoster had increased at 4 weeks without any increase in adverse events. Studies of safety and immunogenicity in this population in response to RZV are ongoing, but the Advisory Committee on Immunization Practices recommends that all persons over age 50 with a history of herpes zoster receive RZV. There is no specific recommendation regarding vaccinating patients less than 50 years of age with a history of herpes zoster, regardless of immune status, given the lack of data in these populations.