b After 1 year of follow-up, patients on HAART with a baseline viral load (VL) of <20 copies/ml showed significantly lower odds of virological rebound to two consecutive VLs of >50 copies/ml than those with baseline VLs of 20 to 39 and 40 to 49 (P < 0.001). The time to virological rebound was also significantly shorter (P < 0.001) for the groups with baseline VLs of 20 to 39 and 40 to 49. T he number of patients failing antiretroviral treatment with low-level viremia (e.g., a viral load [VL] ranging from 40 to 1,000 copies/ml) is increasing (1, 2), and special interest has been shown in the clinical significance of this finding. During the last years of the past decade, commercial assays for measuring viral loads reduced their detection limits (3-6), which shifted from 50 to 40 to 20 copies/ml, depending on the assay (7). Recently, a number of reports (8-12) have focused on the clinical significance of very low-level viremia (e.g., viral-load levels below 20 or between 20 and 50 copies/ml). The use of different assays or a different sample size, and even different baseline characteristics of the studies, may partially explain some of the contradictory findings of the studies. In addition, high variability of the Cobas Ampliprep/Cobas TaqMan v2.0 assay at levels of 20 and 40 HIV copies/ml has been described (13).Since the introduction in our institution of Cobas TaqMan v2.0 (Roche Diagnostics) in June 2009, the lower detection cutoff of 50 copies/ml was shifted to 20 copies/ml, and this new threshold was reported to physicians treating HIV and thus used for making clinical decisions.In this retrospective cohort study, we have investigated the clinical significance of having a viral load between 20 and 50 copies/ml in terms of the odds for a viral-load rebound to more than 50 copies/ml or 400 copies/ml 1 year after testing. When possible, the emergence of resistance was also investigated.All adult HIV patients (Ͼ18 years old) who were on highly active antiretroviral therapy (HAART) with an available follow-up 12 months (median, 12.42 months; interquartile range [IQR], 11.73 to 13.80 months) after a viral-load test result below 50 copies/ml (time zero [T 0 ]) using the Cobas TaqMan v2.0 assay were included. When needed, resistance testing of very low-level viral loads was performed using a concentration step (14) prior to following the standard procedure of the Trugene HIV genotyping kit (Siemens NAD). Two hundred ninety patients met the inclusion criteria, and the pre-T 0 CD4 count, time (in years) with a VL of Ͻ50 before T 0 , number of years on HAART, and type of HAART regimen were retrieved from their medical records. Virological rebound was considered when two consecutive viral loads were recorded. Two definitions of virological rebound were evaluated: (i) rebound to more than 50 copies/ml, confirmed in two consecutive samples, and (ii) rebound to more than 400 copies/ ml, also confirmed in two consecutive samples. The time to virological rebound in months was also recorded. The baseline characteristics were ...

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Nuestro estudio ha evaluado las ventajas de la utilización del kit Sepsityper® para la identificación rápida de microorganismos a partir de hemocultivos positivos, acompañado de la tecnología de espectrometría de masas MALDITOF MS®, en comparación con los métodos tradicionales empleados para el diagnóstico de bacteriemia. Para la identificación del microorganismo en 379 hemocultivos positivos en el Departamento de Microbiología del Hospital Universitario San Cecilio, se aplicó la espectrometría de masas MALDITOF MS® utilizando el sistema Sepsityper® (Bruker) y se comparó con la identificación mediante métodos convencionales (Wider, Vitek II, Api). La correlación de resultados de los dos esquemas diagnósticos fue determinada estadísticamente por el coeficiente de correlación kappa. La distribución de los aislamientos fue de un 24,7 % de Bacilos Gram negativos (BGN) y 75,3 % de microorganismos Cocos Gram positivos (CGP). La concordancia global de resultados fue del 95,8 % en la especie (k = 0,928) y del 98,7 % en el género (k = 0,977), siendo el porcentaje de identificaciones fallidas del 1,3%. Para BGN hubo una concordancia de resultados del 95,2 % (k = 0,928, especie), y 100 % (k = 1, género). Respecto a los CGP, la concordancia fue del 98,2 % en género (k = 0,931), y del 82,5 % (k = 0,627) a nivel de especie. En nuestra experiencia se ha observado una ganancia de al menos 13-23h en la identificación a nivel de especie. La utilización del kit Sepsityper® para la identificación rápida de microorganismos a partir de hemocultivos positivos, acompañado de MALDITOF MS®, muestra una excelente correlación respecto a la identificación realizada a través de la metodología convencional, con una importante disminución del tiempo hasta la identificación. AbstractOur study has evaluated the advantages of using Sepsityper® kit for a fast identification of microorganisms from positive blood cultures, along with the mass spectrometry technology MALDITOF-MS®, compared to traditional methods used for diagnosis of bacteremia. To identify the microorganism isolated from the 379 positive blood cultures (BC +) the Department of Microbiology, University Hospital San Cecilio, MALDITOF-MS® mass spectrometry along with Sepsityper® (Bruker) were applied and it was compared to the conventional methods for the identification of this organism. The correlation of results between these two diagnostic schemes was statistically determined by kappa correlation coefficient. The distribution of the isolates was 24.7% for Gram negative bacilli (GNB) and 75.3% for Gram-positive cocci (GPC). The overall concordance of results was 95.8% within the species (k = 0.928) and 98.7% within the genus (k = 0.977), with a failed-identification percentage of 1.3%. For GNB there was a concordance of results of 95.2% (k = 0.928, species), and 100% (k = 1, genus). Regarding the GPC, the concordance was 98.2% within the genus (k = 0.931), and 82.5% (k = 0.627) at the species level. According to our experience there was a gain of at least 13-23 hours in the identific...