Matrix Matters: Assessment of Commutability among BK Virus Assays and Standards.

Quantitative testing of BK virus (BKPyV) nucleic acid has become the standard of care in transplant patients. While the relationship between interassay harmonization and commutability has been well characterized for other transplant-related viruses, it has been less well studied for BKPyV, particularly regarding differences in commutability between matrices. Here, interassay agreement was evaluated among six real-time nucleic acid amplification tests (NAATs) and one digital PCR (dPCR) BKPyV assay. Differences in the commutability of three quantitative standards was examined across all assays using a variety of statistical approaches. Panels, including 40 samples each of plasma and urine samples previously positive for BKPyV, together with one previously negative plasma sample and four previously negative urine samples, were tested using all assays, with each real-time NAAT utilizing its usual quantitative calibrators. Serial dilutions of WHO, National Institute for Standards and Technology (NIST), and commercially produced (Exact/Bio-Rad) reference materials were also run by each assay as unknowns. The agreement of the clinical sample values was assessed as a group and in a pairwise manner. The commutability was estimated using both relativistic and quantitative means. The quantitative agreement across assays in the urine samples was within a single log10 unit across all assays, while the results from the plasma samples varied by 2 to 3 log10 IU/mL. The commutability showed a similar disparity between the matrices. Recalibration using international standards diminished the resulting discrepancies in some but not all cases. Differences in the sample matrix can affect the commutability and interassay agreement of quantitative BKPyV assays. Differences in commutability between matrices may largely be due to factors other than those such as amplicon size, previously described as important in the case of cytomegalovirus. Continued efforts to standardize viral load measurements must address multiple sources of variability and account for differences in assay systems, quantitative standards, and sample matrices.

Cost-Effective Respiratory Virus Testing.

The timely and accurate diagnosis of respiratory virus infections has the potential to optimize downstream (posttesting) use of limited health care resources, including antibiotics, antivirals, ancillary testing, and inpatient and emergency department beds. Cost-effective algorithms for respiratory virus testing must take into consideration numerous factors, including which patients should be tested, what testing should be performed (for example, antigen testing versus reverse transcription-PCR testing or influenza A/B testing versus testing with a comprehensive respiratory virus panel), and the turnaround time necessary to achieve the desired posttesting outcomes. Despite the clinical impact of respiratory virus infections, the cost-effectiveness of respiratory virus testing is incompletely understood. In this article, we review the literature pertaining to the cost-effectiveness of respiratory virus testing in pediatric and adult patient populations, in emergency department, outpatient, and inpatient clinical settings. Furthermore, we consider the cost-effectiveness of a variety of testing methods, including rapid antigen tests, direct fluorescent antibody assays, and nucleic acid amplification tests.

Sustained virological response to ombitasvir/paritaprevir/ritonavir and dasabuvir treatment for hepatitis C: Real-world data from a large healthcare provider.

Treatment with ombitasvir/paritaprevir/ritonavir and dasabuvir, with or without ribavirin (OPrD ± RBV), was the first interferon-free direct-acting antiviral for hepatitis C virus (HCV) introduced to Israel's national basket of health services in February 2015. Patients with HCV genotype 1 (GT1) and advanced fibrosis (F3-F4) were eligible for treatment in 2015. This study aimed to characterize patients initiating OPrD ± RBV and assess sustained virological response (SVR). A retrospective cohort study was performed using the database of Maccabi Healthcare Services (MHS), a 2-million-member health plan in Israel. The study population included adults who initiated OPrD ± RBV through December 2015 per health basket criteria. A gap in medication fills (>14 days between a fill's run-out and the next fill) was used to estimate adherence. SVR was defined by the viral tests at least 12-week post-treatment. The study population consisted of 403 patients (56.3% male), with a mean age of 60.7 years (SD 11.0). Overall, 71.0% were naïve to prior HCV treatment, and 95.6% were treated with a 12-week regimen. A total of 348 patients (86.4%) completed the regimen in the usual time frame (highly adherent), whereas 8.2% completed with a gap, and 4.7% purchased less than the recommended dose. SVR rates overall and among highly adherent patients were 395/403 (98.0%; 95% CI 96.1-99.1) and 346/348 (99.4%; 95% CI 97.9-99.9), respectively. GT1b patients on 12-week regimens attained SVR rates of 194/196 (fibrosis F3) and 170/176 (cirrhosis). After a first year of provision of OPrD ± RBV with good adherence, high SVR rates were achieved in various patient subgroups and comorbidities.

Cytomegalovirus-Responsive CD8+ T Cells Expand After Solid Organ Transplantation in the Absence of CMV Disease.

Cytomegalovirus (CMV) is a major cause of morbidity and mortality in solid organ transplant recipients. Approximately 60% of adults are CMV seropositive, indicating previous exposure. Following resolution of the primary infection, CMV remains in a latent state. Reactivation is controlled by memory T cells in healthy individuals; transplant recipients have reduced memory T cell function due to chronic immunosuppressive therapies. In this study, CD8+ T cell responses to CMV polypeptides immediate-early-1 and pp65 were analyzed in 16 CMV-seropositive kidney and heart transplant recipients longitudinally pretransplantation and posttransplantation. All patients received standard of care maintenance immunosuppression, antiviral prophylaxis, and CMV viral load monitoring, with approximately half receiving T cell-depleting induction therapy. The frequency of CMV-responsive CD8+ T cells, defined by the production of effector molecules in response to CMV peptides, increased during the course of 1 year posttransplantation. The increase commenced after the completion of antiviral prophylaxis, and these T cells tended to be terminally differentiated effector cells. Based on this small cohort, these data suggest that even in the absence of disease, antigenic exposure may continually shape the CMV-responsive T cell population posttransplantation.

Progress in Quantitative Viral Load Testing: Variability and Impact of the WHO Quantitative International Standards.

It has been hoped that the recent availability of WHO quantitative standards would improve interlaboratory agreement for viral load testing; however, insufficient data are available to evaluate whether this has been the case. Results from 554 laboratories participating in proficiency testing surveys for quantitative PCR assays of cytomegalovirus (CMV), Epstein-Barr virus (EBV), BK virus (BKV), adenovirus (ADV), and human herpesvirus 6 (HHV6) were evaluated to determine overall result variability and then were stratified by assay manufacturer. The impact of calibration to international units/ml (CMV and EBV) on variability was also determined. Viral loads showed a high degree of interlaboratory variability for all tested viruses, with interquartile ranges as high as 1.46 log10 copies/ml and the overall range for a given sample up to 5.66 log10 copies/ml. Some improvement in result variability was seen when international units were adopted. This was particularly the case for EBV viral load results. Variability in viral load results remains a challenge across all viruses tested here; introduction of international quantitative standards may help reduce variability and does so more or less markedly for certain viruses.

First documentation of isoniazid reversion in Mycobacterium tuberculosis.

BACKGROUND: Drug-resistant strains of Mycobacterium tuberculosis are increasing worldwide and pose a major threat to global health. However, it remains unsettled whether drug-resistant mutants are fixed in the bacterial population or if they would revert in the absence of drug pressure. OBJECTIVE: To document the occurrence of isoniazid (INH) reversion in a patient with multidrug-resistant tuberculosis (TB) and investigate its association with fitness cost. DESIGN: Genotypic and phenotypic assays were used to characterize the reversion of INH resistance in isolates from a patient with pulmonary TB. The pre-reversion katG mutation was reconstructed in a pan-susceptible laboratory strain (H37Rv DeltakatG::katG W300G) and tested for susceptibility to INH and oxidative stress. RESULTS: Genotyping and drug susceptibility testing showed that an isogenic strain of M. tuberculosis reverted from an INH-resistant to a susceptible phenotype in the absence of INH therapy. The genotypic basis of this reversion was mapped to the katG codon 300 which reverted from GGG (glycine, G) to a wild-type codon, TGG (tryptophan, W). The H37Rv DeltakatG::katG W300G mutant was resistant to INH, but also showed a deficiency in coping with oxidative stress. CONCLUSION: This study confirms that, in the absence of INH pressure, some INH-resistant mutants will revert to a drug-susceptible phenotype. This finding may have broader implications for INH-resistant strains and for the clinically useful lifespan of INH.

Transplant outcomes and economic costs associated with patient noncompliance to immunosuppression.

We describe factors associated with immunosuppression compliance after kidney transplantation and examine relationships between compliance with allograft outcomes and costs. Medicare claims for immunosuppression in 15 525 renal transplant recipients with at least 1 year of graft function were used to calculate compliance as medication possession ratio. Compliance was categorized by quartiles as poor, fair, good and excellent. We modeled adjusted associations of clinical factors with the likelihood of persistent compliance by multiple logistic regressions (aOR), and estimated associations of compliance with subsequent graft and patient survival with Cox proportional hazards (aHR). Adolescent recipients aged 19-24 years were more likely to be persistently noncompliant compared to patients aged 24-44 years (aOR 1.49 [1.06-2.10]). Poor (aHR 1.80 [1.52-2.13]) and fair (aHR 1.63[1.37-1.93]) compliant recipients were associated with increased risks of allograft loss compared to the excellent compliant recipients. Persistent low compliance was associated with a $12 840 increase in individual 3-year medical costs. Immunosuppression medication possession ratios indicative of less than the highest quartile of compliance predicted increased risk of graft loss and elevated costs. These findings suggest that interventions to improve medication compliance among kidney transplant recipients should emphasize the benefits of maximal compliance, rather than discourage low compliance.

Predictive ability of pretransplant comorbidities to predict long-term graft loss and death.

Whether to include additional comorbidities beyond diabetes in future kidney allocation schemes is controversial. We investigated the predictive ability of multiple pretransplant comorbidities for graft and patient survival. We included first-kidney transplant deceased donor recipients if Medicare was the primary payer for at least one year pretransplant. We extracted pretransplant comorbidities from Medicare claims with the Clinical Classifications Software (CCS), Charlson and Elixhauser comorbidities and used Cox regressions for graft loss, death with function (DWF) and death. Four models were compared: (1) Organ Procurement Transplant Network (OPTN) recipient and donor factors, (2) OPTN + CCS, (3) OPTN + Charlson and (4) OPTN + Elixhauser. Patients were censored at 9 years or loss to follow-up. Predictive performance was evaluated with the c-statistic. We examined 25 270 transplants between 1995 and 2002. For graft loss, the predictive value of all models was statistically and practically similar (Model 1: 0.61 [0.60 0.62], Model 2: 0.63 [0.62 0.64], Models 3 and 4: 0.62 [0.61 0.63]). For DWF and death, performance improved to 0.70 and was slightly better with the CCS. Pretransplant comorbidities derived from administrative claims did not identify factors not collected on OPTN that had a significant impact on graft outcome predictions. This has important implications for the revisions to the kidney allocation scheme.

A retrospective analysis of immunosuppression compliance, dose reduction and discontinuation in kidney transplant recipients.

We describe factors associated with poor compliance and dose reductions and examine the relative impact of compliance, dose reduction and discontinuation on graft outcome. Medicare claims for MMF in 7062 deceased donor renal recipients with at least 1 year of graft function were used to calculate compliance and dose reductions. Compliance was modeled using medication possession ratio to define quartiles for poor, low, medium and high compliance. The relative impact of compliance, dose reduction and discontinuation on graft outcome was assessed with Cox proportional hazards. Pediatric (Age 0-18, Odds ratio = 1.71, 95% CI 1.11-2.63, p = 0.014) and adolescent recipients (19-24, 1.57, 1.23-2.00, p < 0.001) were more likely poorly compliant compared to adults age 25-44. Poor compliance was also associated with physical limitations, hypertension, delayed graft function, rejection, infection and GI conditions. Poor (1.43, 1.11-1.84, p = 0.005) and low (1.46, 1.13-1.88, p = 0.004) compliance was associated with an increased hazard of graft loss as was >50% dose reduction (1.69, 1.15-2.50, p = 0.008) and discontinuation (8.34, 6.85-10.2, p < 0.001). Medication possession ratios lower than the 3-year mean were associated with an increased risk of graft loss. These results may indicate that interventions to improve compliance among kidney transplant recipients should strive for high rather than discourage low compliance.

Nlk is a murine protein kinase related to Erk/MAP kinases and localized in the nucleus.

Extracellular-signal regulated kinases/microtubule-associated protein kinases (Erk/MAPKs) and cyclin-directed kinases (Cdks) are key regulators of many aspects of cell growth and division, as well as apoptosis. We have cloned a kinase, Nlk, that is a murine homolog of the Drosophila nemo (nmo) gene. The Nlk amino acid sequence is 54. 5% similar and 41.7% identical to murine Erk-2, and 49.6% similar and 38.4% identical to human Cdc2. It possesses an extended amino-terminal domain that is very rich in glutamine, alanine, proline, and histidine. This region bears similarity to repetitive regions found in many transcription factors. Nlk is expressed as a 4. 0-kb transcript at high levels in adult mouse brain tissue, with low levels in other tissues examined, including lung, where two smaller transcripts of 1.0 and 1.5 kb are expressed as well. A 4.0-kb Nlk message is also present during embryogenesis, detectable at day E10. 5, reaching maximal steady state levels at day E12.5, and then decreasing. Nlk transiently expressed in COS7 cells is a 60-kDa kinase detectable by its ability to autophosphorylate. Mutation of the ATP-binding Lys-155 to methionine abolishes its ability to autophosphorylate, as does mutation of a putative activating threonine in kinase domain VIII, to valine, aspartic, or glutamic acid. Subcellular fractionation indicates that 60-70% of Nlk is localized to the nucleus, whereas 30-40% of Nlk is cytoplasmic. Immunofluorescence microscopy confirms that Nlk resides predominantly in the nucleus. Nlk and Nmo may be the first members of a family of kinases with homology to both Erk/MAPKs and Cdks.

Phase-resolved fluorescence lifetime measurements for flow cytometry.

A flow cytometer capable of measuring fluorescence lifetimes by the phase shift method has been built and evaluated. Under optimal conditions, the resolution of the fluorescence lifetime measurement is shown to be under 200 picoseconds. Pulse intensity variations are normalized using limiting amplifiers and electronic filtering. Normalization of signal intensities provides a lifetime measurement that is independent of fluorescence intensity over at least a 50-fold (17 dB) range in fluorescence intensity. The fluorescence lifetimes of unbound dye, fluorescent beads, cells stained with ethidium bromide, propidium iodide, and phycoerythrin-conjugated monoclonal antibodies have been measured. The fluorescence lifetimes measured for these particles are well correlated with lifetime measurements made using a standard fluorimeter. Cells stained with ethidium bromide and propidium iodide at various nucleotide-to-dye ratios are shown to exhibit similar behavior to static cuvette measurements. The fluorescence lifetime parameter is also shown to resolve phycoerthyrin fluorescence from propidium iodide fluorescence.

Optical polarization properties of the diffraction spectra from single fibers of skeletal muscle.

The diffraction spectra of laser light from single fibers of skeletal muscle exhibit a large degree of optical depolarization. When the linearly polarized incident laser source is oriented at polarization angles between 0 less than theta less than pi/2 rad with respect to the fiber axis, the diffracted light is elliptically polarized. These results show that the phase angle of the ellipse rotates by as much as 20 degrees when the fiber is stretched from 2.4 to 3.8 microns. To further ascertain that the observed phenomenon is diffraction related, an experiment monitoring the spectra of scattered light in between diffraction orders showed this signal to be significantly more linearly polarized. These results suggest that the degree of elliptical polarization of the diffraction spectra is a sensitive probe of A-band dynamics, including changes of the anisotropic S-2 elements.