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Our qbank for biostatistics contains questions that covers high yield concepts and includes research abstracts. These difficult concepts are very likely to be tested in the real USMLE examination and are good for all three USMLE Steps. Currently, there are 22 questions. We recommend going through the questions twice.
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Explanation covers the high yield concepts that are not tested in the question.
Our qbank for biostatistics contains questions that covers high yield concepts.
Here are two sample questions:
Neutrophil CD64 has been proposed as an early marker of sepsis. This study aims to evaluate the diagnostic utility of neutrophil CD64 for identification of early-onset sepsis in preterm neonates.
The prospective study was conducted in a neonatal intensive care unit between November 2010 and June 2011. Preterm neonates in whom infection was suspected when they were <12 hours of age were enrolled. Complete blood count with differential, blood culture, neutrophil CD11b and CD64 measurement were performed. Receiver operating characteristic curve analysis was performed to evaluate the performance of neutrophil CD64 as biomarker of sepsis.
A total of 158 preterm neonates was enrolled, 88 of whom were suspected infection. The suspected sepsis group was of lesser gestational age (P<0.001) and lower birth weight (P<0.001), compared with controls. The hematologic profiles of the suspected sepsis group were characterized by higher white blood cell count, neutrophil counts and C-reactive protein. The suspected sepsis neonates had significantly higher neutrophil CD64 expression compared with controls. Neutrophil CD64 had an area value under the curve of 0.869 with an optimal cutoff values of 1010 phycoerythrin molecules bound/cell and it had a high sensitivity (82%) and negative predictive value (77.4%). The level of neutrophil CD64 was independent of antibiotic therapy within 24 hours after the onset of sepsis in preterm neonates.
Neutrophil CD64 is a highly sensitive marker for suspected early-onset sepsis in preterm neonates. Our study suggests that neutrophil CD64 may be incorporated as a valuable marker to diagnose infection.
Citation: Du J, Li L, Dou Y, Li P, Chen R, Liu H (2014) Diagnostic Utility of Neutrophil CD64 as a Marker for Early-Onset Sepsis in Preterm Neonates. PLoS ONE 9(7): e102647. doi:10.1371/journal.pone.0102647
Based on the study above, if 10 preterm neonates with suspected sepsis were tested for Neutrophil CD64 then what is the probability that at least one of the patients would test negative?
B. 10 x 0.18
C. 1-(10 x 0.82)
D. 1- 0.82^10
In a research study, the diagnostic performance of Macrophage inhibitory cytokine 1 (MIC-1), CA19.9, CEA and CA242 was evaluated. The figure below shows the data analysis from the study.
Figure. Comparison of the diagnostic performance of serum MIC-1, CA19.9, CEA and CA242 for PDAC. a. Sensitivities and specificities of MIC-1 , CA19.9, CEA and CA242 for the diagnosis of pancreatic ductal adenocarcinoma (PDAC) was compared through the analyses of ROC curves in the discovery group (n = 1307). AUROC curve of serum MIC-1 was much larger than that of CA19.9, CEA and CA242 (P < 0.001). b. The potential of serum MIC-1 for distinguishing CA19.9-negative pancreatic carcinomas from non–pancreatic carcinoma controls including benign pancreas tumors. c. A similar positive rate (present above the bar) of serum MIC-1 (using the cut off value 1000 pg/mL) was observed in patients with PDAC with different CA19.9 levels.(Ref: Ann R Coll Surg Engl. 2013 April; 95(3): 215–221.)
Based on the study, which one of the following is the most accurate diagnostic test for pancreatic ductal adenocarcinoma?