Evaluation of four automated clinical analyzers for the determination of total 25(OH)D in comparison to a certified LC-MS/MS.

OBJECTIVES: The aim of this study was to compare the results of five methods for the determination of total 25(OH)D. For that purpose, two mass spectrometry and three immunoassay methods were used. METHODS: A total of 124 serum samples were analyzed on five different methods (i.e., a reference LC-MS/MS, Cascadion, Lumipulse, Roche Elecsys II and Roche Elecsys III). Analytical performance against LC-MS/MS was evaluated and compared to the Milan models 1 (analytical performance based on the clinical outcome using thresholds of 12, 20 and 30 ng/mL) and 2 (analytical performance based on biological variation). Additionally, imprecision studies and accuracy using NIST SRM972a samples were carried out. RESULTS: Compared to the reference LC-MS/MS method, the Lumipulse and the Roche Elecsys III assays reached the optimal criterion for bias, while the Cascadion met the desirable one. The Roche Elecsys II was not able to reach the minimal criteria. The proportion of correctly classified patients was higher using the Cascadion (95.2%) compared to the three immunoassays. In addition to its better precision, the Cascadion was not impacted by a high concentration of 3-epi-25(OH)D3 compared to the three immunoassays. CONCLUSIONS: Compared to the LC-MS/MS reference method, the Cascadion presented the highest level of concordance at medical decision cut-offs for total 25(OH)D and reached the desirable specification for bias. Moreover, the presence of 3-epi-25(OH)D3 in enriched samples was only problematic in immunoassay methods, and especially considering Roche Elecsys methods. The release of performant fully automated mass spectrometry assays with high throughput might therefore facilitate the wide scale adoption of LC-MS/MS, even in non-specialized clinical laboratories.

Assessment of the Androstenedione Assay on a Roche Analytical Platform and Comparison with Different Methods.

BACKGROUND: D4-androstenedione (D4ASD) is an intermediate hormone of androgen biosynthesis by the gonads and the adrenal glands. The interest in D4ASD concentration assessment resides in diagnostics of androgenic hyperproduction pathologies. Currently, many D4ASD quantification methods are available on the market including immunological methods that remain problematic due to the possible cross-reactivity with endogenous or exogenous steroids. METHODS: Recently Roche® launched a new fully automated instrument for the measurement of D4ASD concentration. In this paper, the criteria of analytical performance (repeatability and intermediate precision) of the D4ASD Roche® assay were assessed and compared with 2 different methods including a radioimmunoassay (RIA) as well as a liquid chromatography tandem mass spectrometry (LC-MS/MS) method. RESULTS: Repeatability and intermediate precision of the D4ASD Roche® were acceptable according to the prede-fined RICOS standard (CV ≤ 7.9%) and the assay showed a good correlation with other assays considering the 95% CI obtained for the slope and the y-intercept. CONCLUSIONS: This method demonstrates acceptable criteria of analytical performance with an intermediate imprecision and a trueness within the fixed acceptance limits.

The free cortisol calculated: correlation with the free cortisol concentrations measured with liquid chromatography-tandem mass spectrometry after equilibrium dialysis and establishment of reference intervals.

BACKGROUND: Changes in cortisol binding globulin (CBG) impact the total serum cortisol concentration and affect the accurate assessment of adrenal function. Free biologically cortisol can be calculated using different equations or directly measured after complicated procedures. METHODS: The free cortisol index (FCI) obtained using the Bonte formula as well as the free cortisol concentration calculated (Coolens equation) were first estimated for 45 healthy workers. The CBG level was determined by a competitive radioimmunoassay and the total cortisol concentration, was measured with an electrochemiluminescent assay. The correlations between FCI, the free cortisol concentrations calculated and the free cortisol levels measured with liquid chromatography-tandem mass spectrometry after equilibrium dialysis were studied for those 45 samples. Reference limits were established on 158 healthy hospital workers and patients with serum samples collected between 7:30 am and 10 am. RESULTS: The FCI as well as the free cortisol concentrations calculated obtained for the 45 samples correlated significantly with the free cortisol levels measured. Although the cortisol and CBG levels were statistically higher in women using contraceptives compared with women not taking them as well as men, the calculated FCI and free cortisol concentrations did not differ between these groups. The medians (P2.5-P97.5) obtained for the 158 healthy workers were respectively 26.4% (12.3-51.6%) and 10.6 nmol/L (4.3-26.7 nmol/L). CONCLUSIONS: This study highlighted a significant correlation between the FCI, the free cortisol concentrations calculated and the free cortisol levels measured with LC-MS/MS, it has also allowed the establishment of reference intervals for calculated FCI and free cortisol.

Severe vitamin D deficiency in patients admitted to the emergency department with severe sepsis is associated with an increased 90-day mortality.

BACKGROUND: The role of vitamin D in the response to infection has been increasingly acknowledged. However, the influence of severe vitamin D deficiency on the outcome of patients admitted for severe sepsis is unknown. Hence, this study aimed to investigate the association between severe vitamin D deficiency and sepsis-related outcomes in patients presenting to the ED. METHODS: This single centre prospective study included patients presenting to the ED with severe sepsis from April 2014 until December 2017. 25-Hydroxy vitamin D (25(OH)D) was measured in a blood sample drawn within 24 hours of admission to the ED, and severe vitamin D deficiency was defined as 25(OH)D <12 ng/mL. 90-day mortality was compared between patients with and without severe vitamin D deficiency by a multivariable analysis adjusting for confounders and according to a Kaplan-Meier survival analysis. RESULTS: 263 patients were initially screened and 164 patients with severe sepsis were included in this study, 18% of whom had septic shock. Severe vitamin D deficiency was present in 46% of patients. The overall 90-day mortality rate was 26.2% and the median length of stay was 14 days. In a logistic regression accounting for sepsis severity and age-adjusted comorbidities, severe vitamin D deficiency was associated with increased mortality (OR=2.69 (95% CI 1.03 to 7.00), p=0.043), and lower chances of hospital discharge (sub-HR=0.66 (95% CI 0.44 to 0.98)). In the subgroup of patients admitted to the intensive care unit, severe vitamin D deficiency was associated with an increased 28-day adjusted mortality (HR=3.06 (95% CI 1.05 to 8.94), p=0.04) and lower chances of discharge (sub-HR=0.51 (95% CI 0.32 to 0.81)). CONCLUSIONS: Severe vitamin D deficiency at ED admission is associated with higher mortality and longer hospital stay in patients with severe sepsis.

Screening for hereditary spherocytosis in daily practice: what is the best algorithm using erythrocyte and reticulocyte parameters?

Hereditary spherocytosis (HS) is the most common inherited chronic haemolytic anaemia in Northern Europe. During the last decade, additional erythrocyte and reticulocyte parameters have been developed on last-generation haematology analysers, leading to many publications about their effectiveness as a HS screening tool. For the first time on an independent cohort, we evaluated and compared the effectiveness of six published algorithms for the screening of HS using the UniCel DxH800 (Beckman-Coulter) and the XN-9000 (Sysmex) and determined which algorithm could be the most suitable in our daily clinical practice. A total of 95 EDTA samples were analysed prospectively on both haematology analysers. These included 11 confirmed HS patients and 84 non-HS patients. The specific reticulocyte parameters used on the DxH800 were mean reticulocyte volume, immature reticulocyte fraction and mean sphered cell volume, and on the XN-9000 were hypohaemoglobinised erythrocytes, microcytic erythrocytes and immature reticulocyte fraction. The three algorithms using parameters specific to Beckman-Coulter analysers provided a sensitivity of 100% with various specificities, ranging from 7.1 to 73.8%. The three algorithms published based on the parameters specific to Sysmex showed much lower performances, i.e. out of the 11 patients with HS, between one to five patients were screened as negative for HS. However, 100% sensitivity and specificity were reached using the EMA binding test concomitantly with those three algorithms. The algorithms using reticulocyte and erythrocyte parameters offered by the recent analysers are promising options as a HS first-tier screening tool. Nevertheless, they must be evaluated by each laboratory on their own analyser before implementation.

Two-site evaluation of the Roche Elecsys Vitamin D total III assay.

OBJECTIVES: The high request for vitamin D testing in the last decades has led manufacturers to develop assays on automated immunoassay platforms. The objective of this study was to evaluate the performance of the new Elecsys Vitamin D total III assay for the measurement of total 25(OH)D. METHODS: A total of 844 serum samples collected in two clinical laboratories were used to evaluate the new Roche Elecsys Vitamin D total III assay. Comparisons with Roche Elecsys Vitamin D total II and liquid chromatography tandem mass spectrometry (LC-MS/MS) were carried out. Additionally, assay imprecision, linearity, matrix effects, biotin interference, cross-reactivity with 24,25(OH)2D3 and 3-epi-25(OH)D3, and outlier rate were evaluated for the Elecsys Vitamin D total III assay. RESULTS: Only the comparison between LC-MS/MS and Roche Elecsys Vitamin D total III achieved the optimal specification for bias (i.e., <3.4%). Imprecision, linearity and matrix effects showed acceptable results. The biotin interference threshold was increased up to 1,200 ng/mL and the outlier rate was low (0.26%). The cross-reactivity with 24,25(OH)2D3 and 3-epi-25(OH)D3 was weak or modest in available patient samples. However, using SRM972a with a high level of 3-epi-25(OH)D3 (enriched) revealed an important cross-reactivity with both Roche Elecsys Vitamin D total II and III assays (+74.7% and +73.7%). CONCLUSIONS: In conclusion, the Roche Elecsys Vitamin D total III assay presents several advantages compared to the previous assay generation: higher biotin interference threshold, broader measuring range, and better comparability with LC-MS/MS. However, the cross-reactivity toward 3-epi-25(OH)D3 is still problematic in high titer samples.

Development and validation of a simple correction method for the measurement of neuron-specific enolase in hemolyzed serum samples.

The Neuron-specific enolase (NSE), a biomarker of neuroendocrine tumors or ischemic brain damage, has limited clinical applicability since its measurement is overestimated by hemolysis. In this study, an NSE correction method was developed for hemolyzed samples. The NSE concentration and the hemolysis index (HI) of serum were measured before and after spiking a hemolysate prepared with red blood cells from the serum-separating tube and extrapolating the NSE value corresponding to a HI of zero. To validate the approach (n = 46), NSE concentrations and HI were measured before (NSE0 and HI0) and after spiking the samples with 50 µL (HIA, NSEA) and 100 µL (HIB, NSEB) of hemolysate. A linear regression analysis was performed between (HIA, NSEA) and (HIB, NSEB). The y-intercept was taken as the corrected NSE concentration (NSEintercept) and compared with NSE0. On the same samples, the equation of Tolan et al. was applied and the corrected values of NSE (NSEcorr) were compared to NSE0. The average bias (±SD) between the NSE0 and the NSEintercept was equal to -3.2% (± 14.3) versus 34.6% (± 19.8) against the NSEcorr. Applying the allowable total error proposed by the European Federation of Laboratory Medicine, 72% of the NSE results were adequately corrected while the reference method corrected only 8.7% of the results. The individualized hemolysis correction method developed is simple, fast, requires one serum-separating tube, provides increased accuracy compared to the method described by Tolan et al. and should improve the quality of patient care.

Comparison of the Quantitative DiaSorin Liaison Antigen Test to Reverse Transcription-PCR for the Diagnosis of COVID-19 in Symptomatic and Asymptomatic Outpatients.

We evaluated the quantitative DiaSorin Liaison severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antigen test in symptomatic and asymptomatic individuals consulting their general practitioners (GPs) during a period of stable intense virus circulation (213/100,000 habitants per day). Leftover reverse transcription-PCR (RT-PCR) positive (n = 204) and negative (n = 210) nasopharyngeal samples were randomly selected among fresh routine samples collected from patients consulting their GPs. Samples were tested on Liaison XL according to the manufacturer's instructions. Equivocal results were considered negative. The overall sensitivity and specificity of the Liaison antigen test compared to RT-PCR were 65.7% (95% confidence interval [CI], 58.9% to 71.9%) and 100% (CI, 97.8% to 100%). Sensitivity in samples with viral loads of ≥105, ≥104, and ≥103 copies/ml were 100% (CI, 96.3% to 100.0%), 96.5% (CI, 91.8% to 98.7%), and 87.4% (CI, 81.3% to 91.5%), respectively. All samples with ≤103 copies/ml were antigen negative. The ratio of antigen concentration to viral load in samples with ≥103 copies/ml was comparable in symptomatic and asymptomatic individuals (P = 0.58). The proportion of RT-PCR-positive participants with a high viral load (≥105 copies/ml) was not significantly higher in symptomatic than in asymptomatic participants (63.9% [CI, 54.9% to 72.0%] versus 51.9% [CI, 41.1% to 62.6%]; P = 0.11), but the proportion of participants with a low viral load (<103 copies/ml) was significantly higher in asymptomatic than in symptomatic RT-PCR-positive participants (35.4% [CI, 25.8% to 46.4%] versus 14.3% [CI, 9.0% to 21.8%]; P < 0.01). Sensitivity and specificity in samples with a viral load of ≥104 copies/ml were 96.5% and 100%. The correlation of antigen concentration with viral load was comparable in symptomatic and asymptomatic individuals.

Pharmacokinetics and target attainment of intravenous posaconazole in critically ill patients during extracorporeal membrane oxygenation.

BACKGROUND: Posaconazole is an antifungal drug used for prophylaxis and treatment of invasive fungal infections. Severe influenza has been identified as a risk factor for invasive pulmonary aspergillosis in critically ill patients. In this population, extracorporeal membrane oxygenation (ECMO) is used as rescue therapy, although little is known about the pharmacokinetics (PK) of posaconazole during ECMO. OBJECTIVES: To determine the PK and target attainment of six patients treated with IV posaconazole under ECMO and to develop a population PK model that can be used to simulate the PTA. METHODS: Critically ill patients treated with posaconazole and ECMO were included in this study. Plasma samples were collected at several timepoints within one dosing interval on two occasions: an early (Day 2-3) and a late (Day 4-7) sampling day. Daily trough concentrations were measured. RESULTS: The median (IQR) AUC0-24, CL and Vd were 34.3 (28.3-37.7) mg·h/L, 8.7 (8.0-10.6) L/h and 389 (314-740) L, if calculated with non-compartmental analysis based on the observed concentrations. All measured trough concentrations were ≥0.7 mg/L and 11/16 were ≥1 mg/L, which are the haematological thresholds for prophylaxis and treatment of invasive aspergillosis, respectively. The targeted PTA (>90%) was attained for prophylaxis but not for treatment. CONCLUSIONS: ECMO does not appear to influence posaconazole exposure compared with haematology patients. However, some trough levels were below the lower limit for treatment. An a priori dose adjustment does not appear to be necessary but drug monitoring is recommended.

Mass Spectrometry for the Monitoring of Lipoprotein Oxidations by Myeloperoxidase in Cardiovascular Diseases.

Oxidative modifications of HDLs and LDLs by myeloperoxidase (MPO) are regularly mentioned in the context of atherosclerosis. The enzyme adsorbs on protein moieties and locally produces oxidizing agents to modify specific residues on apolipoproteins A-1 and B-100. Oxidation of lipoproteins by MPO (Mox) leads to dysfunctional Mox-HDLs associated with cholesterol-efflux deficiency, and Mox-LDLs that are no more recognized by the LDL receptor and become proinflammatory. Several modification sites on apoA-1 and B-100 that are specific to MPO activity are described in the literature, which seem relevant in patients with cardiovascular risk. The most appropriate analytical method to assess these modifications is based on liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). It enables the oxidized forms of apoA-1and apoB-100 to be quantified in serum, in parallel to a quantification of these apolipoproteins. Current standard methods to quantify apolipoproteins are based on immunoassays that are well standardized with good analytical performances despite the cost and the heterogeneity of the commercialized kits. Mass spectrometry can provide simultaneous measurements of quantity and quality of apolipoproteins, while being antibody-independent and directly detecting peptides carrying modifications for Mox-HDLs and Mox-LDLs. Therefore, mass spectrometry is a potential and reliable alternative for apolipoprotein quantitation.

ß-Lactam Dosage Regimens in Septic Patients with Augmented Renal Clearance.

Augmented renal clearance is commonly observed in septic patients and may result in insufficient ß-lactam serum concentrations. The aims of this study were to evaluate potential correlations between drug concentrations or total body clearance of ß-lactam antibiotics and measured creatinine clearance and to quantify the need for drug dosage adjustments in septic patients with different levels of augmented renal clearance. We reviewed 256 antibiotic measurements (512 drug concentrations) from a cohort of 215 critically ill patients who had a measured creatinine clearance of ≥120 ml/min and who received therapeutic drug monitoring of meropenem, cefepime, ceftazidime, or piperacillin from October 2009 until December 2014 at Erasme Hospital. Population pharmacokinetic (PK) analysis of the data was performed using the Pmetrics software package for R. Fifty-five percent of drug concentrations showed insufficient ß-lactam serum concentrations to treat infections due to Pseudomonas aeruginosa There were significant, yet weak, correlations between measured creatinine clearance and trough concentrations of meropenem (r = -0.21, P = 0.01), trough concentrations of piperacillin (r = -0.28, P = 0.0071), concentrations at 50% of the dosage interval (r = -0.41, P < 0.0001), and total body clearance of piperacillin (r = 0.39, P = 0.0002). Measured creatinine clearance adequately explained changes in drug concentrations in population pharmacokinetic models for cefepime, ceftazidime, and meropenem but not for piperacillin. Therefore, specific PK modeling can predict certain ß-lactam concentrations based on renal function but not on absolute values of measured creatinine clearance, easily available for clinicians. Currently, routine therapeutic drug monitoring is required to adjust daily regimens in critically ill patients receiving standard dosing regimens.

Caspofungin dosage adjustments are not required for patients with Child-Pugh B or C cirrhosis.

Background: Controversies remain over caspofungin dosage adjustments in cirrhosis, particularly Child-Pugh (CP) B or C. The product information for of caspofungin recommends a maintenance dose reduction from 50 to 35 mg for patients with CP-B cirrhosis. Objectives: To quantify the impact of cirrhosis and the severity of hepatic impairment on the pharmacokinetics (PK) of caspofungin. Patients and methods: We performed PK studies of a single 70 mg dose of caspofungin in patients with decompensated CP-B (n = 10) or CP-C (n = 10) cirrhosis and of multiple doses in 21 non-cirrhotic ICU patients with hypoalbuminaemia. A Monte Carlo simulation was performed to investigate the impact of a maintenance dose reduction from 50 to 35 mg on the steady-state area under the 24 h concentration-time curve. Results: We observed a marginal reduction of caspofungin clearance in a PK study in patients with decompensated CP-B or CP-C cirrhosis. Dose reduction to 35 mg in cirrhotic patients resulted in lower drug exposure than with the approved dose in non-cirrhotic patients. Conclusions: In contrast to the product information, we recommend giving the full dose of caspofungin regardless of the presence and severity of cirrhosis to avoid a subtherapeutic exposure.

Hydroxyurea (hydroxycarbamide) genotoxicity in pediatric patients with sickle cell disease.

BACKGROUND: Hydroxyurea (HU) reduces the severity of sickle cell disease (SCD) in children; nevertheless, its long-term safety is an important concern. This paper evaluates HU genotoxicity at dose ≤ 30 mg/kg/day after over 2 years of treatment. PROCEDURE: The study included 76 children: 32 SCD patients treated with HU, 27 SCD patients not treated with HU, and 17 unaffected children. HU patients were classified as good or poor responders according to their clinical response. Comet assay allows the comparison of DNA damage between both groups of patients and unaffected children. Maximal concentration (Cmax ) of HU in plasma was determined after drug administration. RESULTS: Mean values of DNA in the comet tail were 5.13 ± 6.84 for unaffected children, 5.80 ± 7.78 for patients with SCD treated with HU, and 5.61 ± 6.91 for patients with SCD not treated with HU. Significant differences were observed between unaffected children and children with SCD. No difference was evident between comets from SCD patients treated and not treated with HU. In the case of HU, mean DNA in the comet tail was significantly lower in good responders than in poor responders: 5.54 ± 7.77 and 6.69 ± 8.43, respectively. Mean Cmax value on plasma was 39.08 ± 15.65 mg/l; N = 31. CONCLUSIONS: SCD increases, slightly but significantly, DNA damage in lymphocytes from patients with SCD. Patients with SCD treated with HU do not present more nucleoid damage than patients with SCD not treated with HU. Good responders to the HU treatment have significantly less nucleoid damage than poor responders. HU treatment at ≤30 mg/kg/day does not expose patients to a genotoxic plasma concentration.

Baseline hepcidin measurement in the differential diagnosis of anaemia for elderly patients and its correlation with the increment of transferrin saturation following an oral iron absorption test.

Background Anaemia is often multifactorial in the elderly, with a frequent association between iron deficiency anaemia (IDA) and anaemia of chronic disease (ACD). The primary objective of our study was to investigate whether baseline hepcidin measurement could be useful for identifying iron deficiency (ID) in anaemic elderly patients. The secondary objective was to assess whether baseline hepcidin concentrations correlated with the relative increase of transferrin saturation (TS) after an oral iron absorption test (OIAT). Methods Blood samples were collected between 7:30 am and 10:00 am in 328 geriatric outpatients, 102 underwent the OIAT. Types of anaemia were classified according biochemical and clinical criteria. TS and hepcidin were measured at baseline and 4 h after the iron dose. The ability of baseline hepcidin measurement to highlight ID in elderly anaemic patients was assessed using a receiver operator curve (ROC) analysis. Correlations between baseline hepcidin levels and the increment of TS following the OIAT were investigated using the Spearman coefficient. Results Among 328 included patients, 78 (23.8%) suffered from anaemia; 13 (4.0%), 19 (5.8%), 27 (8.2%) and 19 (5.8%) patients fulfilled criteria for IDA, IDA/ACD, ACD and unexplained anaemia, respectively. By multivariable analysis, creatinine, C-reactive protein, ferritin, Delta TS and Delta hepcidin were independently associated with baseline hepcidin concentrations. The area under the ROC curve (95% confidence interval) was 0.900 (0.830-0.970) for baseline hepcidin measurement. Baseline hepcidin levels correlated negatively with the relative increase in TS with a Spearman coefficient of -0.742. Conclusions Baseline hepcidin levels could be a useful tool to identify ID in anaemic elderly patients and may predict acute iron response following OIAT.

Comparison of two assays measuring human chorionic gonadotrophin serum concentrations in pregnancy termination and trophoblastic or non-trophoblastic tumours.

BACKGROUND: Differences in human chorionic gonadotrophin (hCG) results provided by the commercial immunoassays reflect the heterogeneity of antibodies and the use of suboptimal standards. As a consequence, the principal forms of hCG and metabolites are differentially detected and the hCG tests are not suited for the same clinical applications. Conflicting results are available in the literature regarding which hCG variants are recognized by the Roche Elecsys hCG + ß test. The aim of our study was to compare the hCG concentrations provided by the Siemens Immulite 2000 test and the Roche test as well as to assess the concordance between both assays. METHODS: In this purpose, 152 samples obtained from women and 44 samples from men were analysed by both tests during the follow-up of pregnancy termination, gestational trophoblastic disease and malignancies. The intermediate precision of the Roche test was also investigated on a pool with a low hCG concentration. RESULTS AND CONCLUSIONS: The hCG concentrations measured with the Roche test were slightly lower compared with the Siemens assay; mean biases of -34.2% and -8% were respectively obtained for hCG values ≤100 UI/L and higher than 100 UI/L. The overall agreement between both assays was 96.1% for women and 97.7% for men. By using an upper reference limit of 3.2 UI/L for women and 1.6 UI/L for men, the Roche test demonstrated a respective concordance of 98.7% and 100%. This test also yielded an excellent precision with a coefficient of variation of 2.8% at a mean hCG concentration of 7 UI/L.

New Regimen for Continuous Infusion of Vancomycin in Critically Ill Patients.

Despite the development of new agents with activity against Gram-positive bacteria, vancomycin remains one of the primary antibiotics for critically ill septic patients. Because sepsis can alter antimicrobial pharmacokinetics, the development of an appropriate dosing strategy to provide adequate concentrations is crucial. The aim of this study was to prospectively validate a new dosing regimen of vancomycin given by continuous infusion (CI) to septic patients. We included all adult septic patients admitted to a mixed intensive care unit (ICU) between January 2012 and May 2013, who were treated with a new vancomycin CI regimen consisting of a loading dose of 35 mg/kg of body weight given as a 4-h infusion, followed by a daily CI dose adapted to creatinine clearance (CrCL), as estimated by the Cockcroft-Gault formula (median dose, 2,112 [1,500 to 2,838] mg). Vancomycin concentrations were measured at the end of the loading dose (T1), at 12 h (T2), at 24 h (T3), and the day after the start of therapy (T4). Vancomycin concentrations of 20 to 30 mg/liter at T2, T3, and T4 were considered adequate. A total of 107 patients (72% male) were included. Median age, weight, and CrCL were 59 (interquartile range [IQR], 48 to 71) years, 75 (IQR, 65 to 85) kg, and 94 (IQR, 56 to 140) ml/min, respectively. Vancomycin concentrations were 44 (IQR, 37 to 49), 25 (IQR, 21 to 32), 22 (IQR, 19 to 28), and 26 (IQR, 22 to 29) mg/liter at T1, T2, T3, and T4, respectively. Concentrations were adequate in 56% (60/107) of patients at T2, in 54% (57/105) at T3, and in 73% (41/56) at T4. This vancomycin regimen permitted rapid attainment of target concentrations in serum for most patients. Concentrations were insufficient in only 16% of patients at 12 h of treatment.

A high-dose aminoglycoside regimen combined with renal replacement therapy for the treatment of MDR pathogens: a proof-of-concept study.

BACKGROUND: Infections caused by MDR Gram-negative (GN) organisms in critically ill patients are a therapeutic challenge. The administration of high-dose aminoglycoside (HDA) therapy coupled with high-flow continuous veno-venous haemodiafiltration (CVVHDF) could allow required high drug peaks to be achieved with acceptable drug elimination. METHODS: All adult patients present on the ICU between October 2009 and July 2014 who had MDR GN sepsis were considered for HDA and high-flow (>45 mL/kg/h) CVVHDF when an isolated pathogen was susceptible or had intermediate susceptibility to aminoglycosides and the patient's condition was not improving with conventional therapy. Optimal antibacterial activity was defined as a peak concentration of at least eight times the MIC. RESULTS: Fifteen patients infected with MDR GN pathogens (11 with Pseudomonas aeruginosa; 10 with abdominal infections and 5 with respiratory infections) were treated with amikacin (n = 11), gentamicin (n = 3) or tobramycin (n = 1) and high-flow CVVHDF. A favourable clinical response was observed in eight (53%) patients, including three in whom microbial eradication was obtained. Six patients were discharged alive from the ICU, and five from the hospital. No renal toxicity was observed among survivors. CONCLUSION: In this cohort of septic patients with MDR GN infections, HDA combined with high-flow CVVHDF represented a valuable therapeutic option. The effectiveness of this approach should be further evaluated in larger studies.

Serum ß-lactam concentrations in critically ill patients with cirrhosis: a matched case-control study.

BACKGROUND & AIMS: The pharmacokinetics of ß-lactam antibiotics have not been well defined in critically ill patients with cirrhosis. METHODS: We reviewed data from critically ill patients with cirrhosis and matched controls in whom routine therapeutic drug monitoring of two broad-spectrum ß-lactam antibiotics (piperacillin/tazobactam and meropenem) had been performed. Serum drug concentrations were measured twice by high-performance liquid chromatography. Antibiotic pharmacokinetics were calculated using a one-compartment model. We considered that therapy was adequate when serum drug concentrations were between 4 and 8 times the minimal inhibitory concentration of Pseudomonas aeruginosa during optimal periods of time for each drug (≥ 50% for piperacillin/tazobactam; ≥ 40% for meropenem). RESULTS: We studied 38 patients with cirrhosis (16 for piperacillin/tazobactam and 22 for meropenem) and 38 matched controls. Drug dosing was similar in the two groups. The pharmacokinetics analysis showed a lower volume of distribution of meropenem (P = 0.05) and a lower antibiotic clearance of piperacillin/tazobactam (P = 0.009) in patients with cirrhosis than in the matched controls. Patients with cirrhosis were more likely than those without cirrhosis to have excessive serum ß-lactam concentrations (P = 0.015), in particular for piperacillin/tazobactam. CONCLUSIONS: Standard ß-lactam antibiotics regimens resulted in excessive serum concentrations in two thirds of the patients with cirrhosis. This was particularly true for piperacillin/tazobactam, probably because of reduced drug clearance.