Optimising cell-based bioassays via integrated design of experiments (ixDoE) - A practical guide

For process optimisation Design of Experiments (DoE) has long been established as a more powerful strategy than a One Factor at a Time approach. Nevertheless, DoE is not widely used especially in the field of cell-based bioassay development although it is known that complex interactions often exist. We believe that biopharmaceutical manufacturers are reluctant to move beyond standard practices due to the perceived costs, efforts, and complexity. We therefore introduce the integrated DoE (ixDoE) approach to target a smarter use of DoEs in the bioassay setting, specifically in optimising resources and time. Where in a standard practice 3 to 4 separate DoEs would be performed, our ixDoE approach includes the necessary statistical inference from only a single experimental set. Hence, we advocate for an innovative, ixDoE approach accompanied by a suitable statistical analysis strategy and present this as a practical guide for a typical bioassay development from basic research to biopharmaceutical industry.

[Determination of irreversibility of clinical brain death. Electroencephalography and evoked potentials]

Principally, in the fourth update of the rules for the procedure to finally determine the irreversible cessation of function of the cerebrum, the cerebellum and the brainstem, the importance of an electroencephalogram (EEG), somatosensory evoked potentials (SEP) and brainstem auditory evoked potentials (BAEP) are confirmed. This paper presents the reliability and validity of the electrophysiological diagnosis, discusses the amendments in the fourth version of the guidelines and introduces the practical application, problems and sources of error.An EEG is the best established supplementary diagnostic method for determining the irreversibility of clinical brain death syndrome. It should be noted that residual brain activity can often persist for many hours after the onset of brain death syndrome, particularly in patients with primary brainstem lesions. The derivation and analysis of an EEG requires a high level of expertise to be able to safely distinguish artefacts from primary brain activity. The registration of EEGs to demonstrate the irreversibility of clinical brain death syndrome is extremely time consuming.The BAEPs can only be used to confirm the irreversibility of brain death syndrome in serial examinations or in the rare cases of a sustained wave I or sustained waves I and II. Very often, an investigation cannot be reliably performed because of existing sound conduction disturbances or failure of all potentials even before the onset of clinical brain death syndrome. This explains why BAEPs are only used in exceptional cases.The SEPs of the median nerve can be very reliably derived, are technically simple and with few sources of error. A serial investigation is not required and the time needed for examination is short. For these reasons SEPs are given preference over EEGs and BAEPs for establishing the irreversibility of clinical brain death syndrome.

Clinical outcome of neurointerventional emergency treatment of extra- or intracranial tandem occlusions in acute major stroke: antegrade approach with wallstent and solitaire stent retriever

BACKGROUND

Acute large cerebral artery occlusions respond poorly to systemic thrombolysis with recombinant tissue plasminogen activator (rTPA) alone. The value of stent retriever-based mechanical thrombectomy in patients with additional extracranial occlusion of the internal carotid artery (ICA), who require acute a priori extracranial stenting in order to reach the intracranial obstruction site, is not well known. We determined the outcome after emergency revascularization in acute stroke with tandem occlusions of the anterior circulation.

METHODS

According to specific inclusion/exclusion criteria, eligible stroke patients with large artery occlusions underwent mechanical recanalization with the Solitaire stent retriever. In case of a tandem occlusion, we performed an acute stenting with the Wallstent before thrombectomy. From October 2009 to March 2011, 50 patients were treated according to this protocol; time frames, clinical data, recanalization rates, and midterm outcome were recorded.

RESULTS

Forty-one patients had a large artery occlusion in the anterior circulation and nine in the posterior circulation. Mechanical recanalization was successful in 35/41 cases (85 %). Six of 41 patients (15 %) died in the acute phase. In 17/41 patients (42 %), thrombectomy was preceded by an emergency stenting in the extracranial portion of the internal carotid artery (ICA). National Institutes of Health Stroke Scale (NIHSS)/modified Rankin Scale (mRS) scores showed significant improvement in both the stenting group and the nonstenting group; there were no significant differences between the groups. At 90 days, 54 % of patients with emergency stenting had a good outcome.

CONCLUSIONS

Acute extracranial stenting with the Wallstent combined with intracranial Solitaire-based thrombectomy is safe and may lead to an improvement in neurological outcome in patients with an otherwise poor prognosis under i.v. thrombolysis alone.

Semantic Event-Related Potential Components Reflect Severity of Comprehension Deficits in Aphasia

Background and objectives. Several cognitive event-related potential (ERP) components such as mismatch negativity, P300, N400, and the late positive component (LPC) have been studied in aphasia. The aim of this study was to determine whether a modified semantic incongruity paradigm can serve as a more graded differentiation of ERP changes in patients with mild versus severe comprehension deficits. Methods. A total of 20 aphasic patients with minor and severe comprehension deficits and 20 young and elder healthy controls were examined while reading 4-word sentences ending in a semantically congruent or noncongruent word. Results. In contrast to young controls and to patients with mild comprehension deficits, aphasic patients with severe comprehension deficits exhibit an early positivity in the time window from 200 to 400 milliseconds and no N400 after the presentation of nonrecurrent semantically incongruent words. Patients with mild comprehension deficits were found to have an N400 with prolonged latency in comparison with the controls. An age effect in the control groups was detected as well. Discussion. Semantic access and integration are performed differently in aphasic subjects with severe comprehension deficits. These differences in lexical—semantic processing must be taken into account in rehabilitation approaches that aim to improve comprehension deficits. Moreover, the findings may contribute to the design of therapy studies by employing a physiological measure that can discriminate among patients at baseline and at the end of an intervention.

Application of a time-varying covariate model to the analysis of CA 19–9 as a biomarker for time-to-progression (TTP) and overall survival (OS) in patients with advanced pancreatic cancer

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Background: It remains unclear whether baseline CA 19–9 or CA 19–9 kinetics during chemotherapy may serve as predictive biomarker in patients (pts) with pancreatic cancer (PC). Methods: Main inclusion criteria for this retrospective multicenter analysis: histologically confirmed diagnosis of PC, treatment with first-line therapy, pre-treatment CA 19–9 level of > 5.2 U/ml. Analysis of CA 19–9 was exclusively performed using the Elecsys® assay (Roche Diagnostics). The effect of the pre- treatment CA 19–9 level on TTP and OS was modelled by Cox proportional hazards regression. The effect of CA 19–9 kinetics was also modelled by Cox proportional hazards regression where CA 19–9 was treated as time-varying covariate. When modelling CA 19–9 we developed univariate and multivariate Cox models where we selected additional predictors (e.g. performance status) using backward elimination performing likelihood ratio tests on a significance level of 0.05. Results: One-hundred and fifteen pts from 5 German centers were included. Median age was 63 years, 12% had locally advanced and 88% metastatic disease; 73 % of the pts were treated within prospective clinical trials. Median baseline CA 19–9 was 1059 U/ml (range 9.5–100000), median pre- treatment bilirubin 0.6 mg/dl. The median TTP in the study population was 4.4 months, median OS 9.4 months. Univariate analysis showed that the pre-treatment CA 19–9 level (as continuous variable, log [CA 19–9]) was significantly associated with TTP (HR 1.24, 95% CI 1.12–1.37, p<0.001) and OS (HR 1.16, 95% CI 1.06–1.28, p=0.002). These associations remained significant also within a multivariate analysis. For CA 19–9 kinetics during chemotherapy, data from 69 pts (TTP) and 84 pts (OS) were available, respectively; log [CA 19–9] kinetics were found to be a significant predictor for TTP in univariate (HR 1.44, 95% CI 1.25–1.67, p<0.001) and multivariate (HR 1.39, 95% CI 1.19–1.62, p<0.001) analyses, and also for OS (univariate: HR 1.34, 95% CI 1.20–1.49, p<0.001; multivariate: HR 1.39, 95% CI 1.23–1.57, p<0.001). Conclusions: According to this new statistical model, CA 19–9 may serve as a useful predictive biomarker in advanced PC.

[Table: see text]

The predictive role of CA 19–9 kinetics for time-to-progression (TTP) and overall survival (OS) in patients receiving palliative first-line chemotherapy for advanced pancreatic cancer

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Background: Previous studies showed contradictory results for a predictive role of CA 19–9 kinetics during chemotherapy in patients (pts) with pancreatic cancer (PC). Methods: We performed a retrospective, multicenter study in order to evaluate the role of CA 19–9 as a biomarker for TTP and OS in PC. Main inclusion criteria: histological confirmed diagnosis of PC, treatment with first-line chemotherapy for advanced disease, pre-treatment CA 19–9 level of > 5.2 U/ml. As CA 19–9 measurements were conducted in different laboratories using different commercial assays, we defined a subgroup of pts where CA 19–9 was assessed exclusively by the Elecsys assay (Roche Diagnostics). For the analysis of CA 19–9 kinetics, at least one follow-up measurement between day 20 and 64 during first-line chemotherapy had to be available. Pts were divided into two subgroups of CA 19–9 responders and non-responders by cut-offs of a 25% and 50% decline, respectively. OS and TTP were estimated with the Kaplan-Meier-Method, differences between the subgroups were analyzed by using the log-rank test. Results: One hundred and eighty-six pts were included, 83 of them were tested with the Elecsys method. Median age was 63 years, 90 % of the pts were treated within prospective clinical trials. Median pre-treatment CA 19–9 was 1076 U/ml (range 5.7–100,000 U/ml), the median bilirubin was 0.6 mg/dl. Median OS and TTP were 9.8 months (mo) and 5.4 mo, respectively. In univariate analysis, pts with a CA 19–9 decline of at least 25% during chemotherapy lived significantly longer (11.9 mo vs. 8.2 mo, p=0.003) and had a significantly prolonged TTP (5.8 mo vs. 4.4 mo, p=0.018) than those with a lower decline or even CA 19–9 increase. Data for the Elecsys-measurements were comparable (OS: 13.4 mo vs. 8.6 mo, p=0.004; TTP: 7.0 mo vs. 2.6 mo, p=0.003). None of the analyses demanding a CA 19–9 drop of at least 50% reached the level of statistical significance. Conclusion: An early CA 19–9 decline of 25% during first-line chemotherapy may predict OS and TTP in pts with advanced PC. Innovative statistical methods are required to improve our understanding of the utility of CA 19–9 as a predictive biomarker in PC.

[Table: see text]

Short-term modulation of the ipsilateral primary sensory cortex by nociceptive interference revealed by SEPs

We studied the modulation of the topographic arrangement of the human ipsilateral primary somatosensory cortex following interference of nociceptive stimuli by means of dipole source analysis. Multichannel somatosensory evoked potentials were obtained by electrical stimulation of digits 1 and 5 of the left hand before, during and after the application of pain to digits 2-4 of the right hand. The primary cortical response of the SEP (N20) was obtained for dipole localization of the representation of the primary sensory cortex receiving input from digits 1 to 5. The 3D-distance between these sides was calculated for further analysis. To account for possible attentional effects recordings were performed while simultaneously to this intervention subjects were asked to turn their attention to the right or left hand in a pseudorandom order. The application of pain induced an expansion of the 3D-distance between digits 1 and 5. Focusing attention to the stimulated limb or the site of the intervention did not yield to an additional effect. Our results provide further evidence for the presence of a quickly adapting interaction between primary somatosensory areas of both hemispheres following an interference of nociceptive stimulation in SEPs. This modifying process is probably mediated by interhemispheric and intercortical connections leading to hyperexcitability of the primary sensory cortex contralateral to that receiving nociceptive input. Spatial attention does not seem to have an impact on this kind of short-term intercortical plasticity.

Interference of tactile and pain stimuli on thalamocortical signal processing in humans revealed by median nerve SEPs

OBJECTIVE

We investigated the interference of tactile and painful stimuli on human early somatosensory evoked potentials (SEPs) including high frequency oscillations (HFOs) to further study thalamocortical processing of somatosensory information.

METHODS

Multi-channel median nerve SEPs were recorded during (1) no interference, (2) sensory interference by tactile stimulation to digits 2 and 3, and (3) application of pain to the same digits. Spatio-temporal source analysis separated brain stem (S1), thalamic (S2) and two cortical sources (S3, S4), which were evaluated for the low (20-450 Hz) and high (450-750 Hz) frequency portion of the signal.

RESULTS

Low frequency SEPs showed a decrease of activity at cortical source S3 during both conditions, while thalamic source S2 was significantly increased during pain interference. HFOs showed an increase of cortical source S3 and in trend of thalamic source S2 and cortical source S4 during both kinds of interference.

CONCLUSIONS

Although the painful stimulus might not be specific for the nociceptive afferents, the present data affirm that at this early stage of sensory information processing within the primary sensory cortex (area 3b, area 1) pain is handled similar to sensory interference.

SIGNIFICANCE

HFOs might represent an intrinsic "somatosensory alerting" system which reacts to both interference stimuli in a similar way, therefore indicating an interference without a qualitative evaluation.

[Severe encephalitis without correlate in MRI]

Encephalitis could be a life-threatening disease depending on localisation and infectious agent. Neuroimaging, especially MRI, is an important component in the diagnosis. The recent investigations demonstrate that diffusion abnormalities are the first and sensitive signs of viral encephalitis. We describe five patients with severe encephalitis with normal MR imaging. Three of five patients were intermittently mechanically ventilated, two of these longer than 4 weeks. The other two patients suffered from a severe psychosyndrome with seriously limited ability to communicate throughout 6 weeks. At the time of first MRI examination all patients were noticeably ill. Four of five patients had at least one follow-up MRI. The MRI examinations included FLAIR sequences and DWI in four of five patients. Contrast-enhancement was detectable in none of our patients. Follow-up examinations revealed that symptoms of encephalitis were noticeably or completely regressive.

Pseudoangiitis bei beidseitiger okulärer Ischämie

BACKGROUND

The term 'frosted branch angiitis' was initially used to describe an idiopathic form of vasculitis in association with panuveitis. It has since also been used to describe the angiographic phenomenon of diffuse leakage along retinal vessels against the background of other ocular and systemic diseases.

METHODS

We describe a 57-year-old male patient with acute bilateral reduction of visual acuity, headaches and absence of any pulse at the temporal arteries. Fluorescence angiography showed bilateral diffuse leakage along all the retinal vessels, which resembled frosted branches. Laboratory parameters and histology were not indicative of vasculitis. Imaging showed complete occlusion of both common carotid arteries and a hypoplastic vertebral artery on the left.

CONCLUSIONS

Ocular ischemia may imitate primarily inflammatory conditions in its angiographic appearance.

A case of cerebral Whipple's disease initially presenting with isolated focal myoclonus

Neurological manifestations in Whipple's disease are highly variable and tend to occur at later stages of the disease. However, isolated, focal neurological symptoms are reported to be rare. Here we describe the successful treatment of a case of cerebral Whipple's disease initially presenting solely with isolated myoclonic jerks of the left hand and forearm evolving to a segmental myoclonus at a later stage. Additionally, we present - to our knowledge - a novel treatment by administration of immunomodulatory therapy (IVIg) in addition to established antibiotics.