Chiefs’ Inquiry Corner – 12/20/2021

December 20, 2021

Chief residents of the NYU Langone Internal Medicine Residency give quick-and-easy, evidence-based answers to interesting questions posed by house staff, both in their clinics and on the wards.

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  Vitamin B12 functions as a cofactor or coenzyme in various biochemical reactions, including DNA synthesis which promotes normal maturation of blood cells. Concurrent hemolysis in patients with vitamin B12 deficiency is a relatively uncommon but well-recognized phenomenon. While its mechanisms are not entirely understood, it is believed that hemolysis is a result of intramedullary destruction of red blood cells from ineffective erythropoiesis secondary to defective DNA and cell maturation. Deficiency of vitamin B12 inhibits purine and thymidylate synthesis. This impairment of DNA synthesis causes erythroblast apoptosis, resulting in ineffective erythropoiesis. Additionally, B12 deficiency can increase the levels of methylmalonic acid and homocysteine. The accumulation of homocysteine can increase hemolysis by oxidative damage and interaction with RBC structural and enzymatic proteins.

References: New insights into erythropoiesis: the roles of folate, vitamin B12, and iron
  There are a number of cardiac biomarkers used in classifying different aspects of cardiac pathology. The BNP and NT-proBNP are measures of myocyte stretch – the prohormone pro-BNP is cleaved into BNP and NT-proBNP. Assays in different clinical settings may measure one or more of these markers. The most potent inducer of BNP transcription is left ventricular wall stretch due to increased pressure or volume. BNP is cleared by a number of organs, including the kidneys. The sensitivity of this test has been demonstrated in a number of studies (such as the Breathing Not Properly Multinational Study) at various cutoff points, approaching 90% or greater. The specificity of the test is less robust (ranging from 60-90% depending on cutoff points). Aside from heart failure, a number of other cardiopulmonary disorders may be associated with an elevated BNP, including acute coronary syndrome, myocarditis, valvular heart disease, hypertrophic cardiomyopathy, atrial fibrillation/flutter, right ventricular dysfunction in the setting of pulmonary disease. Some other comorbidities, including renal dysfunction and critical illness may be associated with higher BNP levels. That being said, the highest values and cutoffs are consistently observed in patients who have systolic dysfunction (particularly symptomatic systolic left ventricular dysfunction).

References: Cardiac Biomarkers and Heart Failure
 The short answer is yes! Barring 2 exceptions, all vaccines can be co-administered with any other vaccine(s). While many of us may not do this in practice to avoid uncomfortable side effects, the CDC encourages co-administration of all needed vaccines in a visit as it increases the likelihood that that person will remain up to date on vaccination if they happen to miss any follow ups.The 2 exceptions are: 1. PCV13 and PPSV23 pneumococcal vaccines (due to improved immune response when they are spaced apart) and 2. The quadrivalent meningococcal conjugate vaccine and PCV13 in patients with anatomic or functional asplenia and/or HIV infection (based on studies showing decreased antibody concentrations to some pneumococcal serotypes when these were co-administered). (Thanks for the clinical question, Noah!)

References: Timing and Spacing of Immunobiologics