Motivación y conocimiento de la solicitud y significado de los resultados del cribado de drogas de abuso en orina / Reasons for the request and knowledge and significance of the results of the drugs of abuse urine screening

Objetivos. Este estudio pretende evaluar el grado de conocimiento que poseen los médicos para solicitar al laboratorio las determinaciones de drogas de abuso en orina (DAU) por inmunoanálisis, concretamente si es confirmar o excluir una impresión diagnóstica y objetivar el grado de conocimiento que poseen sobre el significado del punto de corte. Material y método. Se diseñó una encuesta que constaba de 4 preguntas, 2 haciendo referencia a la motivación de la solicitud de los inmunoanálisis de DAU y 2 al significado del punto de corte. El periodo de recogida fue mayo y junio de 2010 y como requisito de los encuestados solo se consideró que realizasen su trabajo en un servicio de urgencias hospitalario. Resultados. De 244 encuestas, 199 se consideraron válidas. Un 82,9% de los encuestados realizan la solicitud de cribado de DAU siempre o casi siempre para confirmar una impresión diagnóstica y el 17,0% no las utiliza nunca o casi nunca para esta finalidad. Un 68,3% realiza la solicitud siempre o casi siempre para descartar una impresión diagnóstica. Un 31,6% no las utiliza nunca o casi nunca para esta finalidad. Un 51,2% conoce el significado de un resultado positivo y un 49,7% conoce el de un resultado negativo. Conclusiones. La solicitud de pruebas de DAU requiere conocimientos específicos tanto en motivación como para la interpretación de los resultados del análisis. Los laboratorios clínicos deberían implicarse en esta formación (AU)

Objectives. To demonstrate whether the primary reason for requesting the laboratory determinations of drugs of abuse in urine (DAU) for immunoassay is to confirm or exclude a diagnostic impression, and to determine the level of knowledge on the significance of the cut-off value. Material and methods. We designed a survey that consisted of four questions, two referring to the reasons for the request of the DAU immunoassay and two to the significance of the cut-off. The data was collected during May and June 2010, and the only requirement of the respondents was that they worked in a hospital emergency department. Results. Of 244 questionnaires received, 199 were considered valid. A large majority (82.9%) of respondents made the request for DAU screening always or almost always to confirm a diagnostic impression, and 17.0% never or rarely used it for this purpose. Drug abuse screening was always or almost always requested by 68.3% to rule out a diagnostic impression, and31.6% rarely or never used them for this purpose. The significance of a positive result was understood by 51.2%, and 49.7% understood a negative result. Conclusions. Ordering DAU tests requires specific knowledge of the reason as well as to interpret the result. Clinical laboratories should be involved in training the requesters on the significance of DAU screening (AU)

Rheumatoid factor interference in a tacrolimus immunoassay.

Recently, there has been an interest in the use of tacrolimus for the treatment of rheumatoid arthritis (RA). The role of rheumatoid factor (RF) as a cause of immunoassay interferences is well known. This study is the first to investigate the susceptibility of a tacrolimus immunoassay to interference by RF. Tacrolimus apparent concentrations were determined using the antibody conjugated magnetic immunoassay (ACMIA) run on the Dimension RxL Immunoassay System in 100 randomly selected samples previously submitted for routine diagnostic or monitoring of RA in patients not receiving tacrolimus. Fifty of them had an RF concentration exceeding 100 IU/L and 50 had an RF concentration below 20 IU/L. Samples with tacrolimus apparent whole-blood concentrations above 2.3 ng/mL (limit of quantification of the ACMIA assay alleged by the vendor) were considered as potential false positives. No positive tacrolimus result was found among the 50 samples with serum RF < 20 IU/mL. Among the 50 selected samples from patients with RF > 100 IU/mL (RF range 110-2650 IU/mL), 2 were positive for tacrolimus with ACMIA. In both cases, the pretreatment of these samples with an immunoglobulin blocking agent reduced the apparent tacrolimus concentrations to below the limit of detection. This was confirmed using the alternative and reference tacrolimus assays, both of which reported results below their respective limits of detection. The measured human anti-mouse antibodies levels were found to be elevated. These results show that certain patients with positive RF can have false-positive tacrolimus results using the tacrolimus ACMIA-Flex immunoassay on a Dimension RXL analyzer, which was not the case with 2 other techniques. The interference with the tacrolimus ACMIA results was suppressed after preincubation with an immunoglobulin blocking reagent.

[Clinical value of estimated half-life in paracetamol poisoning as a complement to Rumack's nomogram]. / Interés clínico de la semivida de eliminación del paracetamol como complemento al nomograma de Rumack en la valoración de la intoxicación por paracetamol.

BACKGROUND AND OBJECTIVE: Rumack's nomogram is usually used to indicate the treatment with N-acetilcysteine in the paracetamol poisoning, but it has several limitations. Paracetamol half-life elimination (t1/2) is approximately of 2 h with therapeutic doses and it increases to more than 4 h in patients with hepatotoxicity. The aim of this study was to determine the usefulness of estimated paracetamol t1/2 as greater than or inferior to 4 h by using a simple ratio in relation to the development of hepatotoxicity. PATIENTS AND METHOD: 21 patients with paracetamol overdose were admitted to Son Dureta Hospital (Palma de Mallorca) and Clínic Hospital (Barcelona) over 13 months. The estimated t1/2 is calculated using the quotient between 2 plasma paracetamol concentrations separated by 2 or more hours. RESULTS: We found a significant difference (p < 0.005) between the group with hepatotoxicity (n = 3; t1/2 = 8,5 h; range: 3,6 - 8,7 h); and without hepatotoxicity (n = 18; t1/2 = 2,4 h; (range: 1,6 - 4,3 h). We observed an agreement between positive ratio and a t1/2 > 4 h, and negative ratio with t1/2 < 4 h, bearing in mind that the quotient is obtained through mathematical equations. CONCLUSIONS: Rumack's nomogram should be complemented with t1/2 estimation in all cases of paracetamol poisoning, especially with those patients for whom we are not able to determine the time of ingestion at presentation or if there has been a multiple-timepoint ingestion.

Interés clínico de la semivida de eliminación del paracetamol como complemento al nomograma de Rumack en la valoración de la intoxicación por paracetamol / Clinical value of estimated half-life inparacetamol poisoning as a complement to Rumack’s nomogram

FUNDAMENTO Y OBJETIVO: El nomograma de Rumack seutiliza para indicar el tratamiento con el antídoto Nacetilcisteínaen la intoxicación por paracetamol, perotiene varias limitaciones de uso. La semivida de eliminación(t1/2) del paracetamol, que con dosis terapéuticases de unas 2 h, se incrementa hasta más de4 h en caso de hepatotoxicidad. El objetivo de estetrabajo ha sido validar la predicción de hepatotoxicidada partir de la estimación de la t1/2 como superior oinferior a 4 h obtenida mediante un simple cociente.PACIENTES Y MÉTODO: Se ha estudiado a 21 pacientescon sobredosificación de paracetamol que acudierona los Hospitales de Son Dureta de Palma de Mallorcay Clínic de Barcelona durante un período de 13meses. La estimación de la t1/2 se realizó medianteun cociente entre 2 determinaciones consecutivasde paracetamol en plasma, separadas por un intervalode tiempo de 2 h o más.RESULTADOS: Se observó una diferencia significativa(p < 0,005) en la t1/2 entre el grupo con hepatotoxicidad(n = 3; t1/2 mediana de 8,5 h; extremos: 3,6-8,7 h) y el grupo sin hepatotoxicidad (n = 18; t1/2mediana de 2,4 h; extremos: 1,6-4,3 h). Se hallóuna coincidencia entre cociente positivo y t1/2 superiora 4 h, y entre cociente negativo y t1/2 inferior a4 h, teniendo en cuenta que el cociente se obtuvoa través de ecuaciones matemáticas.CONCLUSIONES: Se propone que se complemente elnomograma de Rumack con la estimación de la t1/2en todos los casos de intoxicación por paracetamol enque se planteen dudas respecto a la indicación detratamiento con antídoto, y en aquellos en los que sedesconozca el tiempo transcurrido desde la ingestao cuando ésta haya sido fraccionada

Rumack’s nomogram isusually used to indicate the treatment with N-acetilcysteinein the paracetamol poisoning, but it hasseveral limitations. Paracetamol half-life elimination(t1/2) is approximately of 2 h with therapeutic dosesand it increases to more than 4 h in patients with hepatotoxicity.The aim of this study was to determinethe usefulness of estimated paracetamol t1/2 as greaterthan or inferior to 4 h by using a simple ratio inrelation to the development of hepatotoxicity.PATIENTS AND METHOD: 21 patients with paracetamoloverdose were admitted to Son Dureta Hospital (Palmade Mallorca) and Clínic Hospital (Barcelona)over 13 months. The estimated t1/2 is calculatedusing the quotient between 2 plasma paracetamolconcentrations separated by 2 or more hours.RESULTS: We found a significant difference (p < 0.005)between the group with hepatotoxicity (n = 3; t1/2 =8,5 h; range: 3,6 – 8,7 h); and without hepatotoxicity(n = 18; t1/2 = 2,4 h; (range: 1,6 – 4,3 h). Weobserved an agreement between positive ratio and at1/2 > 4 h, and negative ratio with t1/2 < 4 h, bearingin mind that the quotient is obtained through mathematicalequations.CONCLUSIONS: Rumack’s nomogram should be complementedwith t1/2 estimation in all cases of paracetamolpoisoning, especially with those patientsfor whom we are not able to determine the time ofingestion at presentation or if there has been amultiple-timepoint ingestion (AU)