The effect of the transition to molecular diagnosis on the epidemiology and the clinical characteristics of bacterial gastroenteritis in Northern Israel.

BACKGROUND: The transition to PCR-based diagnosis of bacterial gastroenteritis (BGE) can increase the sensitivity but might reduce the clinical specificity. The aims of this study were (1) to compare the effect of the change from culture to PCR-based diagnostics on the reported incidence and positivity rates of BGE due to Salmonella, Shigella and Campylobacter species and (2) to compare the demographics, medical background, clinical characteristics and pre-analytic variables between cases with PCR-positive, culture-negative samples to cases with PCR-positive, culture-positive samples. METHODS: The study was performed at the Emek Medical Centre that serves a population of 0.5 million people in Northern Israel. The study included two parts: (1) a retrospective cohort study, comparing the incidence and positivity rates of laboratory-diagnosed BGE from January 2016 until December 22nd, 2019 when culture was the sole method to January 2020 until April 2023 when PCR was used; (2) a prospective cohort study, conducted between November 2020 until April 2023 that compared the demographics and clinical characteristics of BGE cases that were diagnosed by PCR alone versus cases that were diagnosed by both PCR and culture. RESULTS: The incidence rate between-periods comparability ratio was only 113% since the incidence rate did not increase during 2020, the first year of the COVID-19 pandemic. The sample positivity rate increased since 2020, with between-periods comparability ratio of 159%. In the second period, the sample positivity rates of culture vs. PCR alone differed between the pathogens and were 90.2%, 63.8% and 54.2% for Salmonella, Campylobacter and Shigella species, respectively (p < 0.001). The following variables were identified as independent predictors of culture positivity: (1) Salmonella infection (O.R. = 10.6, 95% C.I. 3.6-31.1, p < 0.001); (2) Shigella infection (O.R. = 0.46, 95% C.I.0.23-0.93, p = 0.032); (3) time from sample submission to culture (O.R.=0.73, 95% C.I. 0.58-0.92, p = 0.008); (4) the presence of abdominal pain (O.R. = 1.98, 95% C.I. 1.04-3.79, p = 0.038) and the PCR mean Ct value (O.R. = 0.89, 95% C.I.0.85-0.94, p < 0.001). CONCLUSIONS: The use of PCR had led to improved sensitivity, without noticeable decrease in the clinical specificity. This was especially important in the case of the more fastidious organisms.

A study of histologic and immunophenotypical staining patterns in cutaneous lymphoid hyperplasia.

BACKGROUND: Cutaneous lymphoid hyperplasia (CLH) is generally classified according to clinicopathologic entities or put into broad spectrums of B-cell or T-cell predominance or co-dominance. OBJECTIVE: We sought to discern histologic features and immunohistochemical staining patterns in CLH that may form a basis for a histologic classification system. METHODS: We studied the clinical, histologic, immunophenotypical, and molecular characteristics of 24 consecutive patients with CLH. RESULTS: The 24 cases were classified according to characteristic histologic features and immunophenotypical staining patterns as follows: presence of germinal center (GC) cell clusters forming well-defined lymphoid follicles (n = 10); presence of clusters of GC cell clusters not forming well-defined lymphoid follicles (n = 6); persistent arthropod assault type CLH (n = 1); CLH with a prominent histiocytic component (n = 4); and CLH without specific histologic and immunophenotypical features, that is, nonspecific mixed T-cell and B-cell CLH (n = 3). Most of the CLH cases did not demonstrate clonal T-cell receptor and/or immunoglobulin heavy chain gene rearrangements except for 3 cases in which the long-term follow-up was uneventful. LIMITATIONS: There were a limited number of cases in our study. CONCLUSIONS: A classification based on characteristic histologic features and immunophenotypical staining patterns, along with pertinent clinical and molecular data, may enhance the diagnosis of CLH.

Contact hypersensitivity in patients with primary cutaneous lymphoproliferative disorders.

BACKGROUND: One of the suggested causes of primary cutaneous lymphoproliferative disorders is persistent antigenic stimulation. OBJECTIVE: To study the prevalence of contact hypersensitivity in patients with primary cutaneous lymphoproliferative disorders other than mycosis fungoides (MF). MATERIALS AND METHODS: Thirty consecutive patients with primary cutaneous lymphoproliferative disorders other than MF were patch tested to a European Standard & partial metal series. The results were compared with those of 792 consecutive patients with other skin diseases referred to our clinic and a large published series of 9760 healthy individuals from North America. RESULTS: Twenty-two patients with primary cutaneous lymphoma other than MF and eight patients with pseudolymphomas were included in the study. Altogether there were 23 positive patch tests in 13 patients. Only the prevalence of positive patch tests to cobalt (5/30 patients = 17%) was found to be significantly higher in the studied group than in the two control groups (P<0.01 and P=0.05, respectively). The contact hypersensitivity to cobalt and the other allergens, however, could not be related causally to the pathogenesis of the lesions. CONCLUSIONS: The relative prevalence of contact hypersensitivity to cobalt only was found to be increased in a group of primary cutaneous lymphoproliferative disorders, but a causal relationship to the lymphoproliferative disorders could not be established.