Methodological challenges to control for immortal time bias in addressing drug effects in type 2 diabetes

There are multiple biases in using observational studies to examine treatment effects such as those from prevalent drug users, immortal time and drug indications. We used renin angiotensin system (RAS) inhibitors and statins as reference drugs with proven efficacies in randomized clinical trials (RCTs) and examined their effectiveness in the prospective Hong Kong Diabetes Registry using adjustment methods proposed in the literature. Using time-dependent exposures to drug treatments yielded greatly inflated hazard ratios (HR) regarding the treatment effects of these drugs for cardiovascular disease (CVD) in type 2 diabetes. These errors were probably due to changing indications to use these drugs during follow up periods, especially at the time of drug commencement making time-dependent analysis extremely problematic. Using time-fixed analysis with exclusion of immortal time and adjustment for confounders at baseline and/or during follow-up periods, the HR of RAS inhibitors for CVD was comparable to that in RCT. The result supported the use of the Registry for performing pharmacoepidemiological analysis which revealed an attenuated low low-density lipoprotein cholesterol related cancer risk with RAS inhibitors. On the other hand, time-fixed analysis with including immortal time and adjustment for confounders at baseline and/or during follow-up periods, the HR of statins for CVD was similar to that in the RCT. Our results highlight the complexity and difficulty in removing these biases. We call for validations of the methods to cope with immortal time and drug use indications before applying them to particular research questions, so to avoid making erroneous conclusions.     

Resolvin D1 controls inflammation initiated by glutathione-lipid conjugates formed during oxidative stress

Background and purpose:

Inflammation is associated with oxidative stress and local generation of lipid peroxidation-derived aldehydes, such as 4-hydroxy-trans-2-nonenal (HNE). In most tissues, HNE is readily conjugated with glutathione and presently it is unknown whether glutathionyl-HNE (GS-HNE) plays a functional role in inflammation. Here, we sought to determine whether GS-HNE is a mediator of oxidative stress-initiated inflammation and if its actions can be regulated by the anti-inflammatory and pro-resolving lipid mediator, resolvin D1 (RvD1).

Experimental approach:

GS-HNE was administered intraperitoneally to mice and peritoneal lavages were assessed for leukocyte infiltration and lipid mediators were targeted by mediator-lipidomics. RvD1 was administered to mice treated with GS-HNE and leukocyte infiltration was assessed in the peritoneum. Superoxide production and CD11b modulation were measured in isolated human polymorphonuclear leukocytes incubated with GS-HNE.

Key results:

GS-HNE (1–10 µg) evoked infiltration of Gr-1⁺ leukocytes into the peritoneum to form an inflammatory exudate. With isolated human polymorphonuclear leukocytes, GS-HNE stimulated both superoxide generation and CD11b expression. Among the lipid mediators, both cyclooxygenase- and lipoxygenase-derived pro-inflammatory eicosanoids, including prostaglandin E₂, leukotriene B₄ and cysteinyl leukotrienes, were generated in exudates of mice injected intraperitoneally with GS-HNE. RvD1, given i.v. in doses as low as 0.01–10.0 ng, sharply reduced GS-HNE-stimulated leukocyte infiltration (∼30–70%).

Conclusions and implications:

Glutathione conjugates of HNE, derived during oxidative stress, are pro-inflammatory in vivo. RvD1 protects against this oxidative stress-initiated inflammation.This article is part of a themed issue on Mediators and Receptors in the Resolution of Inflammation. To view this issue visit http://www3.interscience.wiley.com/journal/121548564/issueyear?year=2009     

Frozen Red Blood Cells in Transfusion

Red blood cells (RBCs) can be cryopreserved with shelf life of 10 years. However, shelf life of deglycerolized RBCs in conventional open system is just 24 hours, resulting in sporadic use of Frozen RBC (FS-RBC). Recently Naval Blood Research Laboratory (NBRL) method using ACP 215 (ACP^™ 215 Haemonetics Cell Processing System) has been introduced, where shelf life of deglycerolized RBC is 14 days. FS-RBC unit is prepared from single blood donation, which needs to be glycerolized and deglycerolized. NBRL method using ACP 215 in FS-RBC is described. Deglycerolized unit weighed between 325–350 gm with haemoglobin of 15–18 gm/dl and freeze- thaw- wash RBC recovery of 87%. Transfusion of deglycerolized RBC offered advantages such as elimination of need of crossmatching in emergent situations and reduction of transfusion reactions. FS-RBC by NBRL method using ACP 215 has advantages such as long shelf life, meeting unexpected high blood demand in mass casualties situations or availability of rare blood group requirement of individual patient. FS-RBC can be a potential candidate for Indian Armed Forces Blood programme for uninterrupted blood supply during peace and war.Key Words: Frozen red blood cell, Cryopreservation, Blood transfusion, Armed forces blood programme     

Seroprevalence of Cytomegalovirus among Voluntary Blood Donors

Background

Primary cytomegalovirus (CMV) infection in immunocompetent host is self limiting infection, leading to latency of virus. However congenital CMV and CMV infections in immunocompromised patients are associated with high morbidity and mortality. Transfusion transmitted-cytomegalovirus (TT-CMV) infection in low birth weight neonate and immunocompromised transfusion recipients is being increasingly reported. Studies recommended transfusion of CMV free or CMV safe blood in prevention of TT-CMV. In this background, the study was undertaken to assess the CMV seroprevalence in blood donor.

Methods

A prospective study was conducted in which 431 voluntary blood donors were screened for CMV IgG and IgM by EIA (Enzyme Immuno Assay).

Result

A total of 379 (87.9 %) voluntary blood donors were seropositive for CMV IgG. There was no statistical difference of CMV seropositivity and age. Further, seven (1.6%) subjects were both CMV IgM and IgG seropositive.

Conclusion

High seroprevalence of CMV in our donor population is a threat to the blood safety. Strategies in reducing the risk of TT- CMV are discussed. Use of prestorage leucodepleted ‘CMV safe’ blood components along with judicious use of blood is recommended in prevention of TT-CMV in high risk recipients.Key Words: Cytomegalovirus, Transfusion transmitted infections, Blood donors, Leucodepletion     

Acute paretic syndrome in juvenile White Leghorn chickens resembles late stages of acute inflammatory demyelinating polyneuropathies in humans

Background

Sudden limb paresis is a common problem in White Leghorn flocks, affecting about 1% of the chicken population before achievement of sexual maturity. Previously, a similar clinical syndrome has been reported as being caused by inflammatory demyelination of peripheral nerve fibres. Here, we investigated in detail the immunopathology of this paretic syndrome and its possible resemblance to human neuropathies.

Methods

Neurologically affected chickens and control animals from one single flock underwent clinical and neuropathological examination. Peripheral nervous system (PNS) alterations were characterised using standard morphological techniques, including nerve fibre teasing and transmission electron microscopy. Infiltrating cells were phenotyped immunohistologically and quantified by flow cytometry. The cytokine expression pattern was assessed by quantitative real-time PCR (qRT-PCR). These investigations were accomplished by MHC genotyping and a PCR screen for Marek's disease virus (MDV).

Results

Spontaneous paresis of White Leghorns is caused by cell-mediated, inflammatory demyelination affecting multiple cranial and spinal nerves and nerve roots with a proximodistal tapering. Clinical manifestation coincides with the employment of humoral immune mechanisms, enrolling plasma cell recruitment, deposition of myelin-bound IgG and antibody-dependent macrophageal myelin-stripping. Disease development was significantly linked to a 539 bp microsatellite in MHC locus LEI0258. An aetiological role for MDV was excluded.

Conclusions

The paretic phase of avian inflammatory demyelinating polyradiculoneuritis immunobiologically resembles the late-acute disease stages of human acute inflammatory demyelinating polyneuropathy, and is characterised by a Th1-to-Th2 shift.     

An onset advantage without a preview benefit: neuropsychological evidence separating onset and preview effects in search

Visual search is facilitated if half the distractors are presented as a preview prior to the presentation of the target and second set of distractors--the preview benefit [Watson, D. G., & Humphreys, G. W. Visual marking: Prioritizing selection for new objects by top-down attentional inhibition of old objects. Psychological Review, 104, 90-122, 1997]. On one account, the preview advantage is due to automatic capture of attention by the onsets in the second, search display [Donk, M., & Theeuwes, J. Visual marking beside the mark: Prioritizing selection by abrupt onsets. Perception & Psychophysics, 93, 891-900, 2001]. We provide a neuropsychological test of this assertion. We examined onset capture and preview benefits in search in a group of neuropsychological patients with unilateral parietal damage. We demonstrate a normal pattern of performance when patients detected targets defined by onsets relative to those defined by offsets, irrespective of whether the onset target fell contra- or ipsilateral to the lesion. In contrast, there was a normal preview benefit in search only for ipsilesional targets, and preview search was impaired in the contralesional field. The data demonstrate that the preview benefit can dissociate from the onset advantage in search, and that onsets remain strongly weighted for attention even in the contralesional field of patients with parietal lesions.     

The problem of obesity among adolescents in Hong Kong: a comparison using various diagnostic criteria

Background  

Obesity is now a global epidemic. In this study, we aimed to assess the rates of obesity using several major diagnostic criteria in Chinese school adolescents in Hong Kong.