The Alpha-Defensin Prosthetic Joint Infection Test Has Poor Validity for Native Knee Joint Infection

BackgroundThe alpha-defensin test known as Synovaure has been very effective in diagnosis of prosthetic joint infections (PJIs). Being able to easily and accurately differentiate septic and inflammatory arthropathies in native joints would improve diagnostic workup and management. We tested the ability of an alpha-defensin test to distinguish septic from inflammatory or crystalline arthropathy in the native knee.Methods40 native knee joint fluid specimens were tested with cell count, fluid analysis, and culture and alpha-defensin testing. We determined the sensitivity and specificity of the alpha-defensin test using culture-positive fluid as the gold standard for septic arthropathy and positive crystals as the gold standard for crystalline arthropathy.ResultsThe Synovasure PJI test had 100% specificity for septic arthritis coupled with a 28% false-positive rate when applied to native knee aspirations. False-positive rate was 5.3 times higher in patients with crystals found in the joint fluid.ConclusionAlpha-defensin testing, in the form of the Synovasure PJI test, has a high-false-positive rate when used to distinguish septic and inflammatory arthritis in the native knee joint. Future work will need to determine the sensitivity and specificity of the newer native joint panel. Clinicians should be cognizant of the specific alpha-defensin test used when sampling native knee synovial fluid.     

Impaired Induction of the Apoptosis-Protective Protein Bcl-xL in Activated PBMC from Asymptomatic HIV-Infected Individuals

Progression to AIDS in asymptomatic HIV-infected individuals is characterized by a gradual but progressive loss of CD4⁺ T cells. While the mechanisms underlying this decline are currently unknown, recent evidence suggests that these cells are abnormally sensitive to apoptosis in response to activation signals. Recent work has implicated downregulation of Bcl-2 with the increased spontaneous apoptosis in lymphocytes from HIV-infected patients. We have evaluated the roles of the apoptosis-protective proteins Bcl-2 and Bcl-x in stimulated PBMC from asymptomatic HIV-infected and HIV-uninfected individuals. We found that Bcl-2 was constitutively expressed in PBMC from both HIV-infected and uninfected samples. However, Bcl-x induction was delayed and responses were decreased in stimulated HIV-infected samples. Additionally, single-cell intracellular staining of Bcl-x revealed a significant inverse correlation between PWM-induced Bcl-x expression and apoptosis (r = –0.695, P = 0.005). This was confirmed at the single-cell level in direct experiments when stimulated cells were sorted based on Bcl-x induction and then measured for apoptosis. Furthermore, low Bcl-x expression was not due to reduced lymphocyte activation following PWM stimulation. Our data indicate that the induction of Bcl-x is markedly impaired in asymptomatic HIV-infected patients and that stimuli which induce inadequate expression of Bcl-x are associated with increased levels of apoptosis in these cells.     

Thymic masses on MR imaging

MR imaging is an excellent technique for identifying and defining the extent of thymic tumors. T1-weighted spin-echo MR images (e.g., 600/15 [TR/TE]) best demonstrate tumor extent, and T2-weighted images (e.g., 2500/90 [TR/TE]) help differentiate "cystic" from solid thymic masses. Cyst formation and/or hemorrhage appear as areas of high signal intensity (greater than that of fat) on T2-weighted images. Focal areas of low signal intensity (less than that of muscle) correspond pathologically to fibrous capsules and septa, air, or calcification. In this report, the MR appearance of the normal thymus is reviewed briefly, and the gamut of abnormal thymic masses on MR is illustrated.     

Stent Scraping for Histology: An Alternative Method for Obtaining Tissue to Rule out Neoplasia

Despite improvement in diagnostic modalities, confirmation of a histologic diagnosis of cancer of the biliary tree and pancreas remains elusive. Attempts to collect positive cytology specimens from vigorous brushings or washings obtained at endoscopy or percutaneously are often unsuccessful. In our unit, we have increased the yield by obtaining tissue scraped from prostheses that have been previously placed in either the bile duct or the pancreatic duct. The stents are first flushed with saline to collect cytology specimens, after which, they are bisected and scraped, and these contents are prepared in a manner similar to that used to prepare biopsy samples. Twelve of 16 scraped samples, 9 bile duct and 3 pancreas, were positive for adenocarcinoma. The cytology specimens were positive in only 4 of the 12. We recommend this method of sampling from material contained within prostheses as an adjunct when previous brushings, washings, or biopsies are negative.     

Endoscopic stenting and sphincterotomy of the minor papilla in symptomatic pancreas divisum: results and complications

Pancreas divisum has been postulated as a cause of acute pancreatitis and a chronic pain syndrome in a small subgroup of patients and can be treated with endoscopic dorsal pancreatic duct stent placement and minor papilla sphincterotomy. Twenty patients (9 with at least one attack of idiopathic pancreatitis, and 11 with severe pancreatic-type pain) were treated endoscopically. Dorsal duct stents were placed in 19 patients with subsequent needle knife sphincterotomy of the minor papilla over the stent. Clinical response was judged by comparison of symptoms (using a 0-to-l0 scale and the patient's overall assessment). The symptom score improved from 9.3 to 5.1 in the pancreatitis group and from 9.3 to 5.7 in the pain group. A good clinical response was observed in 3 of 7 patients in the pancreatitis group and in 6 of 11 in the pain group at a mean follow-up of 22 months. Complications of sphincterotomy were limited to pancreatitis in 6 patients (29%), 5 mild and 1 moderate according to published criteria. No patient required more than 4 days hospitalization. Two of 39 stents migrated into the pancreas, and another stent fractured and remained lodged in the pancreas. Eight of 9 patients evaluated demonstrated new morphologic duct changes on follow-up pancreatograms. Endoscopic stenting and sphincterotomy of the minor papilla are feasible and may be effective in some patients with pancreas divisum but carries a significant complication rate. The subjective improvement in patients with chronic pain warrants further controlled study.