Diagnostic performance of fluorescence microscopy with a tetramethylrhodamine isothiocyanate filter in identifying renal amyloidosis.

BACKGROUND: Renal amyloidosis (RA) has a worldwide incidence of 5-13 cases per million person-years and is expected to rise in upcoming years due to growing awareness, plus improvement of diagnostic modalities. Diagnosing RA remains challenging, especially when encountering very small, focal, or early amyloid deposits. Since delays in diagnosis portends poor prognosis, high morbidity, and mortality, it is crucial to evaluate the performance of commonly used diagnostic modalities. This is the first study that presents a full picture of the diagnostic performance of fluorescence microscopy (FM) with a tetramethylrhodamine isothiocyanate (TRITC) filter to diagnose RA in general and stratified by compartments. MATERIALS AND METHODS: A retrospective double-blind diagnostic accuracy study of FM-TRITC filter was performed. The presence or absence of amyloid in the vascular, interstitial, and glomerular compartments was established in 316 representative Congo red-stained core biopsies with an FM-TRITC filter. This was contrasted with polarized microscopy (PM) showing apple-green birefringence as the gold standard. Sensitivity, specificity, positive and negative predictive values, likelihood ratios, and the receiver operating characteristic (ROC) curve were obtained using STATA13. RESULTS: The prevalence of RA was 6.01%, comparable with that reported in the literature. Reciprocity with regard to the location and pattern of fluorescence and birefringence between the two diagnostic modalities was seen. The FM-TRITC filter has a sensitivity of 100%, specificity of 97.64%, and a positive and negative predictive value of 73.08% and 100%, respectively. The positive likelihood ratio was 42.37, and the negative was 0.00. Overall accuracy was 97.78%. The area under the ROC curve was 0.98. The Diagnostic performance of the FM-TRITC filter stratified by compartments is shown in Table 1. The area under the ROC curve was 0.99, 0.98, and 0.99 for the vascular, interstitial, and glomerular compartment, respectively. All patients with RA (n = 19) were correctly identified; this included one new case, one case with small and focal amyloid, and two early cases with less dense amyloid where birefringence was ambiguous by PM. DISCUSSION: The FM-TRITC filter is a highly accurate, sensitive, specific, with excellent predictive values, time-efficient, easy to perform, and suitable to reproduce diagnostic modality for RA. It can accurately rule out RA in all compartments, and in most cases concomitant use of PM should not be indispensable. The diagnosis of vascular, interstitial, and glomerular amyloid deposits can be done using only the FM-TRITC filter with Congo red-stained slides. Exceptionally, a few cases of interstitial amyloidosis could be overdiagnosed due to interferences (e.g. artefacts), these cases could be further assessed with a second diagnostic modality if positive fluorescence is seen. Routine use of the FM-TRITC filter can aid in the diagnosis of early RA, even when the deposits are inconspicuous by PM.

Discriminación entre hiperplasia prostática benigna y cáncer de próstata mediante el uso de PSA index en consulta externa de urología / Discrimination between benign prostatic hyperplasia and prostate cancer by means of PSA index in urology outpatient consult

Objetivo. El antígeno prostático específico es utilizado en el diagnóstico de patologías prostáticas. No existe un estudio en Perú que proponga un punto de corte de PSA index para discriminar entre cáncer de próstata e hiperplasia prostática benigna para la indicación de biopsia prostática. Actualmente, se emplean diferentes puntos de corte basados en estudios internacionales. Material y métodos. Se realizó un estudio de validación diagnóstica de PSA index para discriminar entre ambas entidades en pacientes con un PSA total entre 4,0 ng/ml y 9,9 ng/ml. Fueron incluidos 356 pacientes con diagnóstico de hiperplasia prostática benigna o cáncer de próstata mediante biopsia prostática. Se evaluó la sensibilidad, especificidad, los valores predictivos y los cocientes de probabilidad de los valores de PSA index de 15 hasta 25%. Se graficó la curva ROC. Resultados. Un PSA index de 17% posee mejores valores de sensibilidad (87,8%), especificidad (62,2%) y valores predictivos (valor predictivo positivo de 62,4% y valor predictivo negativo de 87,4%) respecto a otros para disminuir el número de biopsias negativas. El cociente de probabilidad positivo fue 2,3 y el cociente de probabilidad negativo fue 0,1. El área bajo la curva fue 0,75 [IC 95%, 0,71 a 0,79]. Conclusión. Se sugiere un PSA index de 17% como punto de corte para discriminar entre hiperplasia prostática benigna y cáncer de próstata en pacientes que acuden a consulta ambulatoria con un PSA total entre 4,0 ng/ml y 9,9 ng/ml. Se recomienda este valor si se desea reducir el número de biopsias prostáticas negativas (AU)

Objective. The prostate specific antigen is used in the diagnosis of prostate diseases. In Peru, there are no studies that suggest a cut-off point of PSA index to discriminate between benign prostatic hyperplasia and prostate cancer as indicator for prostate biopsy. Based on international studies different cut-off points are used. Material and methods. A diagnostic test was performed to determine the validity of PSA index to discriminate between these two entities in patients with a total PSA between 4.0 ng/ml and 9.9 ng/ml. All 356 patients included were diagnosed of benign prostatic hyperplasia or prostate cancer by prostate biopsy. The sensitivity, specificity, predictive values and likelihood ratios of PSA index cut-off points from 25% to 15% were evaluated. The ROC curve was drawn. Results. A PSA index cut-off point of 17% has better values of sensitivity (87.8%), specificity (62.2%) and predictive values (positive predictive value of 62.4% and negative predictive value of 87.4%) compared to others to decrease the number of negative biopsies. The positive likelihood ratio was 2.3 and the negative 0.1. The area under the curve was 0.75 [IC 95%, 0.71 to 0.79]. Conclusion. We suggest a PSA index of 17% as cut-off point to discriminate between benign prostatic hyperplasia and prostate cancerin the urology outpatient consult of patients with a total PSA between 4.0 ng/ml and 9.9 ng/ml. We recommend this value as it could reduce the number of negative biopsies (AU)

¿Schwannoma gástrico de crecimiento rápido o tumor del estroma gastrointestinal?: presentación de caso clínico y revisión de la literatura / A rapidly-growing gastric schwannoma or GIST?: A case report and literature review

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