Reliability Of Diagnostic Methods Research Articles

Two sensitivity orders applied to the comparison of ROC curves

The main aim of this article is to propose a conceptual support for ROC curves within the general field of inequalities by applying the theory of majorization of vectors. For our purpose, we will use the concept of sensitivity associated with a vector in which have been recently published in literature. Based on the sensitivity concept we first define an order between two vectors that we will call strong order sensitivity. Secondly, we will define a weak version of the previous order that enables us to expand the range of ROC curves that are comparable in absolute terms. Finally, we will apply the results to compare medical diagnostic procedures using ROC curves where we propose a new index of the reliability of diagnostic methods.

Highly simple and visual colorimetric detection of Brucella melitensis genomic DNA in clinical samples based on gold nanoparticles

Control of Malta fever caused by Brucella melitensis (B. melitensis) in humans depends on the reliability of diagnostic methods used for detection and identification of bacteria. In this study, we described a gold nanoparticles–DNA probes (AuNP–DNA probes) hybridization assay for detecting B. melitensis and its differentiation from other members of Brucella spp. in clinical samples. In this detection method, AuNP–DNA probes were hybridized in a tail-to-tail fashion with BMEII0466 sequence, which is specific to B. melitensis. When hybridization occurred in samples containing B. melitensis genomic DNA, it resulted in the formation of a complex and the solution color shifted from red to purple; therefore, visual detection is possible with the naked eye. The efficacy of AuNP–DNA probe hybridization assay was evaluated from genomic DNA of strains of B. melitensis and non-Brucella spp., and also genomic DNA from clinical samples. The results demonstrated that the main characteristics of this system include easy and rapid operation with high sensitivity and specificity. Therefore, no expensive techniques and equipments are necessary. This method can be employed as a regular diagnostic tool for B. melitensis in clinical samples.

Clinical implications of hepatitis B virus mutations: recent advances.

Hepatitis B virus (HBV) infection is a major cause of acute and chronic hepatitis, and of its long-term complications. It is the most variable among DNA viruses, mostly because of its unique life cycle which includes the activity of error-prone enzyme, reverse transcriptase, and the very high virion production per day. In last two decades, numerous research studies have shown that the speed of disease progression, reliability of diagnostic methods and the success of antiviral therapy and immunization are all influenced by genetic variability of this virus. It was shown that mutations in specific regions of HBV genome could be responsible for unwanted clinical outcomes or evasion of detection by diagnostic tools, thus making the monitoring for these mutations a necessity in proper evaluation of patients. The success of the vaccination programs has now been challenged by the discovery of mutant viruses showing amino acid substitutions in hepatitis B surface antigen (HBsAg), which may lead to evasion of vaccine-induced immunity. However, the emergence of these mutations has not yet raised concern since it was shown that they develop slowly. Investigations of HBV genetic variability and clinical implications of specific mutations have resulted in significant advances over the past decade, particularly in regard to management of resistance to antiviral drugs. In the era of drugs with high genetic barrier for resistance, on-going monitoring for possible resistance is still essential since prolonged therapy is often necessary. Understanding the frequencies and clinical implications of viral mutations may contribute to improvement of diagnostic procedures, more proper planning of immunization programs and creating the most efficient therapeutic protocols.

Orthopoxvirus Detection in Environmental Specimens during Suspected Bioterror Attacks: Inhibitory Influences of Common Household Products

After terrorists attacked the United States in 2001, the appearance of letters and other objects containing powdery substances with unknown potentials for biological threat focused attention on the speed, sensitivity, and reliability of diagnostic methods. This study summarizes the abilities and limitations of real-time PCR, electron microscopy (EM), and virus isolation when used to detect potential bioweapons. In particular, we investigated the inhibitory influences of different common household products present in environmental specimens on PCR yield, EM detection, and virus isolation. We used vaccinia virus as a model for orthopoxviruses by spiking it into specimens. In the second part of the study, we describe modifications of diagnostic methods to overcome inhibitory effects. A variety of PCR amplification enhancers, DNA extraction protocols, and applications of internal controls were evaluated to improve diagnostic simplicity, speed, and reliability. As a result, we strongly recommend using at least two different frontline techniques in parallel, e.g., EM and PCR. A positive result obtained by any one of these techniques should be followed by a biological method to confirm the putative diagnosis. Confirmatory methods include virus isolation followed by an agent-specific immunofluorescence assay to confirm the presence of replication-competent particles.