Diagnostic testing, which presumably included an AFB culture of the excisional lymph node material, was negative. Without any further testing, we can conclude that the pre-test probability that this patient has TB is high. A biopsy of a lymph node demonstrates necrotizing granulomatous inflammation. His laboratory markers suggest an acute phase response. In the above patient story, our patient is an otherwise healthy 23-year-old man who lives in a TB-endemic region, who presents with a chronic history of fevers, weight loss, and lymphadenopathy. Thus, the interpretation of that diagnostic test result must include a knowledge of pre-test probability i.e. When the pretest probability for disease X is low, then a positive test result is most likely a false positive (assuming an imperfect specificity). If the pretest probability is high for disease X, then a negative diagnostic test for disease X is most likely a false negative (assuming an imperfect sensitivity). As such, their positive predictive values and negative predictive values are dependent on pre-test probability. Not a single medical diagnostic test has perfect sensitivity and specificity. Only then can you come up with a thoughtful management approach. For those students, I’ve attempted to translate that question into a Bayesian formula that they can relate to: “What is the pre-test probability that this patient has X?”īy knowing who your patient is, you can derive their pre-test probability for a certain disease process. While most trainees grasp the concept, others-who are often highly analytical, fail to do so. The answer to that question helps you build a personal rapport with the patient, understand his/her values, develop a relevant differential diagnosis, and formulate an evidence-based management approach. On the first day of class, I stress to my students that the single most important question to try and answer with every new patient encounter is: “Who is this patient?” I’m an Associate Professor in the Division of Infectious Diseases at Johns Hopkins where I have the great fortune to co-direct the Microbiology/Infectious Diseases course for the first-year medical students. Empiric antituberculous therapy was administered, and the patient made a full recovery. He determined the patient’s syndrome to be most consistent with Mycobacterium tuberculosis infection based upon the patient’s history, prolonged syndrome and clinical presentation, diagnostic results (both positive and negative), and lack of epidemiologic risk for alternate etiologies. The physician was thus required to rely upon his clinical judgment to develop a treatment plan. An excisional biopsy showed necrotizing granulomatous inflammation, but it was otherwise unrevealing for infectious or malignant etiologies. A chest computed tomography scan showed right-sided paratracheal and hilar lymphadenopathy. Laboratory examination revealed a hemoglobin o f 10.3 g/dL, white blood cell count of 5.2 × 10 9/L, erythrocyte sedimentation rate of 90 mm/h, a negative human immunodeficiency virus (HIV) test, and a normal biochemical evaluation. He had no pertinent animal or social exposures, and he had no significant travel history. The patient was born and raised in Turkey but had always lived in urban regions. The pattern of staining on the two blots (HSV-1 and HSV-2) is dictated by the number and identity of the HSV proteins to which the patient's immune system has antibody.Defining Clinical Excellence in Adult Infectious Disease Practice was published by affiliates of the Miller Coulson Academy of Clinical Excellence highlighting the following patient care story:Ī 23-year-old man presented to a hospital in Turkey with 18 months of fever, weight loss, and significant cervical lymphadenopathy. Antibodies, which bind to the viral proteins, are detected by an enzyme-mediated color change. The strips of paper or "blots" containing separated fixed proteins from either HSV-1 or HSV-2 are incubated with the patient's serum. HSV1 and HSV2 proteins from detergent lysates ("Bernstein's lysate") of HSV infected cells are separated by electrophoresis and transferred to nitrocellulose paper. For accurate seroconversion determination, the acute and convalescent samples should be drawn at least 12 -16 weeks apart. The detection of HSV1 and HSV2 IgG class antibodies by Western blot in acute and convalescent serum.
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