Diagnostic accuracy of loop-mediated isothermal amplification as a near-patient test for meningococcal disease in children: An observational cohort study

Background: Diagnosis of meningococcal disease relies on recognition of clinical signs and symptoms that are notoriously non-specific, variable, and often absent in the early stages of the disease. Loop-mediated isothermal amplification (LAMP) has previously been shown to be fast and effective for the molecular detection of meningococcal DNA in clinical specimens. We aimed to assess the diagnostic accuracy of meningococcal LAMP as a near-patient test in the emergency department.

Methods: For this observational cohort study of diagnostic accuracy, children aged 0-13 years presenting to the emergency department of the Royal Belfast Hospital for Sick Children (Belfast, UK) with suspected meningococcal disease were eligible for inclusion. Patients underwent a standard meningococcal pack of investigations testing for meningococcal disease. Respiratory (nasopharyngeal swab) and blood specimens were collected from patients and tested with near-patient meningococcal LAMP and the results were compared with those obtained by reference laboratory tests (culture and PCR of blood and cerebrospinal fluid).

Findings: Between Nov 1, 2009, and Jan 31, 2012, 161 eligible children presenting at the hospital underwent the meningococcal pack of investigations and were tested for meningococcal disease, of whom 148 consented and were enrolled in the study. Combined testing of respiratory and blood specimens with use of LAMP was accurate (sensitivity 89% [95% CI 72-96], specificity 100% [97-100], positive predictive value 100% [85-100]; negative predictive value 98% [93-99]) and diagnostically useful (positive likelihood ratio 213 [95% CI 13-infinity] and negative likelihood ratio 0·11 [0·04-0·32]). The median time required for near-patient testing from sample to result was 1 h 26 min (IQR 1 h 20 min-1 h 32 min).

Interpretation: Meningococcal LAMP is straightforward enough for use in any hospital with basic laboratory facilities, and near-patient testing with this method is both feasible and effective. By contrast with existing UK National Institute of Health and Care Excellence guidelines, we showed that molecular testing of non-invasive respiratory specimens from children is diagnostically accurate and clinically useful.

A comparison of three methods for detecting KRAS mutations in formalin-fixed colorectal cancer specimens.

BACKGROUND: KRAS mutation testing is required to select patients with metastatic colorectal cancer (CRC) to receive anti-epidermal growth factor receptor antibodies, but the optimal KRAS mutation test method is uncertain. METHODS: We conducted a two-site comparison of two commercial KRAS mutation kits - the cobas KRAS Mutation Test and the Qiagen therascreen KRAS Kit - and Sanger sequencing. A panel of 120 CRC specimens was tested with all three methods. The agreement between the cobas test and each of the other methods was assessed. Specimens with discordant results were subjected to quantitative massively parallel pyrosequencing (MPP). DNA blends were tested to determine detection rates at 5% mutant alleles. RESULTS: Reproducibility of the cobas test between sites was 98%. Six mutations were detected by cobas that were not detected by Sanger, and five were confirmed by MPP. The cobas test detected eight mutations which were not detected by the therascreen test, and seven were confirmed by MPP. Detection rates with 5% mutant DNA blends were 100% for the cobas and therascreen tests and 19% for Sanger. CONCLUSION: The cobas test was reproducible between sites, and detected several mutations that were not detected by the therascreen test or Sanger. Sanger sequencing had poor sensitivity for low levels of mutation.

Test stimulus characteristics determine the perceived speed of the dynamic motion aftereffect

Using a speed-matching task, we measured the speed tuning of the dynamic motion aftereVect (MAE). The results of our Wrst experiment, in which we co-varied dot speed in the adaptation and test stimuli, revealed a speed tuning function. We sought to tease apart what contribution, if any, the test stimulus makes towards the observed speed tuning. This was examined by independently manipulating dot speed in the adaptation and test stimuli, and measuring the eVect this had on the perceived speed of the dynamic MAE. The results revealed that the speed tuning of the dynamic MAE is determined, not by the speed of the adaptation stimulus, but by the local motion characteristics of the dynamic test stimulus. The role of the test stimulus in determining the perceived speed of the dynamic MAE was conWrmed by showing that, if one uses a test stimulus containing two sources of local speed information, observers report seeing a transparent MAE; this is despite the fact that adaptation is induced using a single-speed stimulus. Thus while the adaptation stimulus necessarily determines perceived direction of the dynamic MAE, its perceived speed is determined by the test stimulus. This dissociation of speed and direction supports the notion that the processing of these two visual attributes may be partially independent.