Update on the role of pathology and laboratory medicine in diagnosing periprosthetic infection.

Technological and implant design advances have helped reduce the frequency of aseptic total joint arthroplasty failure, but periprosthetic joint infections (PJI) remain a clinical important problem with high patient morbidity. Misinterpreting PJI as aseptic mechanical loosening commonly leads to unsatisfactory revision arthroplasty, persistent infection, and poor long-term results. While there is no single "gold standard" diagnostic test for PJI, recent collaborative efforts by Orthopaedic and Infectious Disease Societies have developed algorithms for diagnosing PJI. However, the efficacy of individual tests as well as diagnostic thresholds are controversial. We review the recommended thresholds for commonly used screening tests as well as tissue histopathology and confirmatory tests to diagnose periprosthetic infection. We also update lesser-known laboratory tests, and we briefly summarize rapidly evolving molecular tests to diagnose periprosthetic infection. Pathologists hold a critical role in assisting with PJI diagnosis, maintaining laboratory test quality and interpreting test results. Collaboration between clinicians and pathologists is essential to provide optimal patient care and reduce the burden of PJI.

Highly sensitive detection of Staphylococcus aureus directly from patient blood.

BACKGROUND: Rapid detection of bloodstream infections (BSIs) can be lifesaving. We investigated the sample processing and assay parameters necessary for highly-sensitive detection of bloodstream bacteria, using Staphylococcus aureus as a model pathogen and an automated fluidic sample processing-polymerase chain reaction (PCR) platform as a model diagnostic system. METHODOLOGY/PRINCIPAL FINDINGS: We compared a short 128 bp amplicon hemi-nested PCR and a relatively shorter 79 bp amplicon nested PCR targeting the S. aureus nuc and sodA genes, respectively. The sodA nested assay showed an enhanced limit of detection (LOD) of 5 genomic copies per reaction or 10 colony forming units (CFU) per ml blood over 50 copies per reaction or 50 CFU/ml for the nuc assay. To establish optimal extraction protocols, we investigated the relative abundance of the bacteria in different components of the blood (white blood cells (WBCs), plasma or whole blood), using the above assays. The blood samples were obtained from the patients who were culture positive for S. aureus. Whole blood resulted in maximum PCR positives with sodA assay (90% positive) as opposed to cell-associated bacteria (in WBCs) (71% samples positive) or free bacterial DNA in plasma (62.5% samples positive). Both the assays were further tested for direct detection of S. aureus in patient whole blood samples that were contemporaneous culture positive. S. aureus was detected in 40/45 of culture-positive patients (sensitivity 89%, 95% CI 0.75-0.96) and 0/59 negative controls with the sodA assay (specificity 100%, 95% CI 0.92-1). CONCLUSIONS: We have demonstrated a highly sensitive two-hour assay for detection of sepsis causing bacteria like S. aureus directly in 1 ml of whole blood, without the need for blood culture.

The New Zealand black mouse as a model for the development and progression of chronic lymphocytic leukemia.

BACKGROUND: Similar to a subset of human patients who progress from monoclonal B lymphocytosis (MBL) to chronic lymphocytic leukemia (CLL), New Zealand Black (NZB) mice have an age-associated progression to CLL. The murine disease is linked to a genetic abnormality in microRNA mir-15a/16-1 locus, resulting in decreased mature miR-15a/16. METHODS: Spleens of aging NZB were analyzed for the presence of B-1 cells via flow cytometry and for the presence of a side population (SP) via the ability of cells to exclude Hoechst 33342 dye. The SP was assayed for the presence of hyperdiploid B-1 clones and for the ability to differentiate into B-1 cells in vitro and transfer disease in vivo. In addition, enhanced apoptosis of chemoresistant NZB B-1 cells was examined by restoring miR-16 levels in nutlin-treated cells. RESULTS: Aging NZB mice develop a B-1 expansion and clonal development that evolves from MBL into CLL. An expansion in SP is also seen. Although the SP did contain increased cells with stem cell markers, they lacked malignant B-1 cells and did not transfer disease in vivo. Similar to B-1 cells, splenic NZB SP also has decreased miR-15a/16 when compared with C57Bl/6. Exogenous addition of miR-15a/16 to NZB B-1 cells resulted in increased sensitivity to nutlin. CONCLUSION: NZB serve as an excellent model for studying the development and progression of age-associated CLL. NZB SP cells do not seem to contain cancer stem cells, but rather the B-1 stem cell. NZB B-1 chemoresistance may be related to reduced miR-15a/16 expression.

Granular acute lymphoblastic leukemia in adults: report of a case and review of the literature.

The diagnosis of granular acute lymphoblastic leukemia (ALL) can be problematic as the cytoplasmic granules found in many blast cells may mimic those seen in acute myelogenous leukemia (AML). This rare variant of B-cell ALL is more commonly diagnosed in children, but may occur in adults. We report a case of granular B-ALL in a 56-year-old female and review the literature.

Prognostic significance of pronormoblasts in erythrocyte predominant myelodysplastic patients.

Recent studies of acute erythroleukemias have reaffirmed DiGuglielmo's syndrome (M6a, myeloblast-predominant) and disease (M6b, pronormoblast-predominant). M6c (mixed myeloblast/pronormoblast) has also been described. However, MDS is still defined according to the percentage of myeloblasts (% myeloblasts) without including the pronormoblast count. A 20-year retrospective study was performed to identify cases demonstrating >or=50% erythrocytic component and <30% calculated blasts (FAB exclusion criteria) without underlying cause (96 cases). Pronormoblast and myeloblast counts and other variables were analyzed as possible explanatory variables of the variations in survival. Considered alone, increasing % myeloblasts and/or percentage of pronormoblasts (% pronormoblasts) were significant predictors of decreasing survival. When all variables were considered as a multivariate group, the best fitting statistical model for predicting survival was a function of age, % pronormoblasts, IPSS cytopenias, platelet count, and percentage erythrocytic component. Of these, % pronormoblasts was by far the most significant. Nonappearance of % myeloblasts in this model is indicative of high correlations of this count with other variables.

Pattern of recruitment of immunoregulatory antigen-presenting cells in malignant melanoma.

The mechanism by which the immune system of a tumor-bearing host acquires tolerance toward tumor antigens is still elusive. Antigen-presenting cells (APCs) are critical regulators of the decision between immune response and tolerance. APCs that express the tryptophan-degrading enzyme indoleamine 2,3-dioxygenase (IDO) have been found to inhibit T-cell responses both in vitro and in vivo. We hypothesized that malignant tumors exploit this mechanism by recruiting IDO-expressing APCs to the tumor-draining lymph nodes. To test this hypothesis, archival tissues and records of 26 cases of lymph node dissection for invasive cutaneous melanoma were obtained. IDO immunohistochemistry was performed on 14 cutaneous tumors and 328 regional lymph nodes. Abnormal accumulations of IDO-positive cells with a monocytoid or plasmacytoid morphology were identified in the perisinusoidal regions of draining lymph nodes in 45% of nodes studied. Recruitment of IDO-positive cells was seen in nodes with and without malignancy. We hypothesize that these IDO-positive APCs may contribute mechanistically to acquired tolerance to tumor antigens. Immunostaining of tumor-draining lymph nodes for abnormal accumulation of IDO-expressing cells might thus constitute an adverse prognostic factor and could contribute to the decision process and the appropriate care of patients with this deadly disease.

Acute leukemia.

This article provides a review of the acute leukemias with updated basic and practical information. The main emphasis is on techniques used to arrive at the correct diagnosis. Although morphology and cytochemistry were the mainstays of diagnosis in the past, new developments in immunophenotyping, cytogenetics, molecular biology, and in vitro assays have improved the understanding of this disease dramatically and enable the identification of new entities with distinct clinicobiologic features.