Multicenter clinical experience with non-invasive cell-free DNA screening for monosomy X and related X-chromosome variants.

OBJECTIVE: We aimed to investigate how the presence of fetal anomalies and different X chromosome variants influences Cell-free DNA (cfDNA) screening results for monosomy X. METHODS: From a multicenter retrospective survey on 673 pregnancies with prenatally suspected or confirmed Turner syndrome, we analyzed the subgroup for which prenatal cfDNA screening and karyotype results were available. A cfDNA screening result was defined as true positive (TP) when confirmatory testing showed 45,X or an X-chromosome variant. RESULTS: We had cfDNA results, karyotype, and phenotype data for 55 pregnancies. cfDNA results were high risk for monosomy X in 48/55, of which 23 were TP and 25 were false positive (FP). 32/48 high-risk cfDNA cases did not show fetal anomalies. Of these, 7 were TP. All were X-chromosome variants. All 16 fetuses with high-risk cfDNA result and ultrasound anomalies were TP. Of fetuses with abnormalities, those with 45,X more often had fetal hydrops/cystic hygroma, whereas those with "variant" karyotypes had different anomalies. CONCLUSION: Both, 45,X or X-chromosome variants can be detected after a high-risk cfDNA result for monosomy X. When there are fetal anomalies, the result is more likely a TP. In the absence of fetal anomalies, it is most often an FP or X-chromosome variant.

Turner syndrome-omphalocele association: Incidence, karyotype, phenotype and fetal outcome.

OBJECTIVE: Omphalocele is known to be associated with genetic anomalies like trisomy 13, 18 and Beckwith-Wiedemann syndrome, but not with Turner syndrome (TS). Our aim was to assess the incidence of omphalocele in fetuses with TS, the phenotype of this association with other anomalies, their karyotype, and the fetal outcomes. METHOD: Retrospective multicenter study of fetuses with confirmed diagnosis of TS. Data were extracted from a detailed questionnaire sent to specialists in prenatal ultrasound. RESULTS: 680 fetuses with TS were included in this analysis. Incidence of small omphalocele in fetuses diagnosed ≥12 weeks was 3.1%. Including fetuses diagnosed before 12 weeks, it was 5.1%. 97.1% (34/35) of the affected fetuses had one or more associated anomalies including increased nuchal translucency (≥3 mm) and/or cystic hygroma (94.3%), hydrops/skin edema (71.1%), and cardiac anomalies (40%). The karyotype was 45,X in all fetuses. Fetal outcomes were poor with only 1 fetus born alive. CONCLUSION: TS with 45,X karyotype but not with X chromosome variants is associated with small omphalocele. Most of these fetuses have associated anomalies and a poor prognosis. Our data suggest an association of TS with omphalocele, which is evident from the first trimester.

First trimester screening with biochemical markers and ultrasound in relation to non-invasive prenatal testing (NIPT).

Non-invasive prenatal testing (NIPT) is often erroneously received as a diagnostic procedure due to its high discriminatory power in the field of fetal trisomy 21 diagnosis (wording: "NIPT replaces amniocentesis"). Already a look at the methodology of NIPT (statistical gene dose comparison of a primarily maternofetal DNA mixture information at selected sites of the genome) easily reveals that NIPT cannot match the gold standard offered by cytogenetic and molecular genetic analysis procedures from the matrix of the entire human genome (origin: vital fetal cells), neither in diagnostic breadth nor in diagnostic depth. In fact, NIPT in fetal medicine in its current stage of development is a selective genetic search procedure, which can be applied in primary (without indication) or secondary (indication-related) screening. Thus, NIPT competes with established search procedures for this field. Here, the combined nuchal translucency (NT) test according to Nicolaides has become the worldwide standard since 2000. The strength of this procedure is its broad predictive power: NT addresses not only the area of genetics, but also the statistically 10 times more frequent structural fetal defects. Thus, NIPT and NT have large overlaps with each other in the field of classical cytogenetics, with slightly different weighting in the fine consideration. However, NIPT without a systematic accompanying ultrasound examination would mean a step back to the prenatal care level of the 1980s. In this respect, additional fine ultrasound should always be required in the professional application of NIPT. NIPT can thus complement NT in wide areas, but not completely replace it.

LECANDUS study (LEsion CANdidate Detection in UltraSound Data): evaluation of image analysis algorithms for breast lesion detection in volume ultrasound data.

PURPOSE: This study aims at developing and evaluating a prototype of a lesion candidate detection algorithm for a 3D-US computer-aided diagnosis (CAD) system. METHODS: Additionally, to routine imaging, automated breast volume scans (ABVS) were performed on 63 patients. All ABVS exams were analyzed and annotated before the evaluation with different algorithm blob detectors characterized by different blob-radiuses, voxel-sizes and the quantiles of blob filter responses to find lesion candidates. Lesions found in candidates were compared to the prior annotations. RESULTS: All histologically proven lesions were detected with at least one algorithm. The algorithm with optimal sensitivity detected all cancers (sensitivity = 100 %) with a very low positive predictive value due to a high false-positive rate. CONCLUSIONS: ABVS is a new technology which can be analyzed by a CAD software. Using different algorithms, lesions can be detected with a very high and accurate sensitivity. Further research for feature extraction and lesion classification is needed aiming at reducing the false-positive hits.

Predictors of Residual Tumor in Breast-Conserving Therapy.

BACKGROUND: Breast-conserving therapy is considered to be the standard treatment for early breast tumors (T1-T2). In up to 82 % of breast-conserving surgery, tumor cells were still found to be present at or near the cut edge of the surgical specimen after surgery. Thus, it is of clinical need to identify tumors at high probability for reexcision in the preoperative setting. METHODS: A total of 686 patients with invasive or in situ breast cancers and primary breast-conserving surgery were included. In 169 cases (24.6 %), breast-conserving therapy was either incomplete or the presence of residual tumor could not be assessed. By univariate analysis, the following parameters were associated with increased probability for reexcision: carcinoma in situ component next to the invasive tumor (p < 0.001), lower age (p = 0.025), premenopausal status (p = 0.033), tumor size (p < 0.001), multifocality (p < 0.001), involved lymph nodes (p = 0.006) and lymphovascular invasion (p < 0.001), differentiation (p = 0.002), and overexpression of the Her2/neu receptor (p = 0.004). The variables with the strongest impact on the reexcision probability in multivariate analyses were tumor size and histology (both p < 0.001), followed by multifocality (p = 0.002) and an accompanying carcinoma in situ (p = 0.004). Lymphovascular invasion (p = 0.016) and age (p = 0.047) also were significantly associated with increased reexcision probability in multivariate analyses. A nomogram for predicting residual tumor in breast-conserving therapy was developed. CONCLUSIONS: The clinical and pathological parameters associated with increased reexcision rates will help to assess an optimized surgical margin, to decrease reexcision rates, and therefore to improve patient care and the quality of life for patients.

Evaluation of an automated breast 3D-ultrasound system by comparing it with hand-held ultrasound (HHUS) and mammography.

PURPOSE: Automated three-dimensional (3D) breast ultrasound (US) systems are meant to overcome the shortcomings of hand-held ultrasound (HHUS). The aim of this study is to analyze and compare clinical performance of an automated 3D-US system by comparing it with HHUS, mammography and the clinical gold standard (defined as the combination of HHUS, mammography and-if indicated-histology). METHODS: Nine hundred and eighty three patients (=1,966 breasts) were enrolled in this monocentric, explorative and prospective cohort study. All examinations were analyzed blinded to the patients´ history and to the results of the routine imaging. The agreement of automated 3D-US with HHUS, mammography and the gold standard was assessed with kappa statistics. Sensitivity, specificity and positive and negative predictive value were calculated to assess the test performance. RESULTS: Blinded to the results of the gold standard the agreement between automated 3D-US and HHUS or mammography was fair, given by a Kappa coefficient of 0.31 (95% CI [0.26;0.36], p < 0.0001) and 0.25 (95% CI [0.2;0.3], p < 0.0001), respectively. Our results showed a high negative predictive value (NPV) of 98%, a high specificity of 85% and a sensitivity of 74% based on the cases with US-guided biopsy. Including the cases where the lesion was seen in a second-look automated 3D-US the sensitivity improved to 84% (NPV = 99%, specificity = 85%). CONCLUSION: The results of this study let us suggest, that automated 3D-US might be a helpful new tool in breast imaging, especially in screening.

Particleboards Bonded by an Imidazole-Based Adhesive System.

Particleboards with different combinations of the adhesive material imidazole, citric acid, and sorbitol were produced. Softwood sawdust from a Swedish sawmill was mixed with an aqueous solution of the chemicals and then dried to 0% moisture content prior to pressing. The boards were pressed to a target density of 700 kg m-3 at either 200 °C or 220 °C for 10 min. The hygroscopic and mechanical properties of the boards were clearly better at 220 °C than 200 °C for all used chemical combinations. A combination of imidazole (14.4 wt%) and citric acid (11.3 wt%) led to the best results, where the thickness swelling after 24 h of water immersion was 6.3% and the internal bonding strength was 0.57 MPa. The modulus of rupture and modulus of elasticity were 3.3 MPa and 1.1 GPa, respectively. Cyclic accelerated weathering showed exceptional stability with a thickness change after boiling and drying of only 2.1% compared to the initial dry thickness. This study indicates that the presence of imidazole leads to greatly improved hygroscopic properties and good internal bonding strength when used in particleboards.

Aneuploidy screening during pregnancy by a three-dimensional Advanced First Trimester Screening model: description of the AFS-3D algorithm.

BACKGROUND: A novel screening method for fetal aneuploidies was developed, in which nuchal translucency (NT), pregnancy-associated plasma protein-A (PAPP-A), and free-ß human chorionic gonadotropin (free-ß hCG) are placed into a three-dimensional scatter plot. Likelihood ratios are directly inferred from the ratio of already observed healthy and diseased fetuses. This method is called 'Three-dimensional Advanced First trimester Screening' (AFS-3D). It was aimed to develop and test a new algorithm based on the results of previous studies. METHODS: A new static-sized sphere model was developed. Several scaling factors of the axes and the optional application of the modifications 'simulation' (SIM) and 'empty sphere positive' were tested on 15,227 data sets. An additional examination was performed on a second collective (n = 458). RESULTS: The application of the new AFS-3D model with static-sized spheres, a re-sampled ∆NT axis by a scaling factor of 0.125, and the application of SIM and Empty Box Positive resulted in a marked improvement of the test performance (area under curve, AUC = 0.9668). Analogous results (AUC = 0.9807) were found for the second test collective. CONCLUSIONS: This novel approach is promising and should be tested on a larger, independent collective.

Predictors of resectability in breast-conserving therapy.

BACKGROUND: Our goal is to identify subgroups of women undergoing breast-conserving therapy (BCT) who are at increased risk for requiring a secondary surgical procedure, and to identify tumor and patient profiles that will allow surgeons to anticipate the need for taking larger margins when removing the tumor. METHODS: One hundred female patients who had palpable, invasive carcinomas of the breast, and had undergone a primary BCT, were included in the study. Of these, all women (n = 25) who had incomplete resections, or questionable margins of resection, had to undergo re-excisions. RESULTS: Patients who had multifocal disease, accompanying ductal carcinoma in situ, involvement of regional lymph nodes, high-grade breast cancer (Grade 3 vs. 1/2), lympho-vascular invasion or negative hormone-receptor-status, were significantly more likely to have undergone incomplete removal of tumor tissue-these patients thus required a secondary surgery. CONCLUSION: The clinical and pathological predictors described above indicate that surgery in breast cancer patients meeting these criteria require larger safety margins to minimize the incidence rate of re-excision at a later date.

Is Fetal Hydrops in Turner Syndrome a Risk Factor for the Development of Maternal Mirror Syndrome?

Mirror syndrome is a rare and serious maternal condition associated with immune and non-immune fetal hydrops after 16 weeks of gestational age. Subjacent conditions associated with fetal hydrops may carry different risks for Mirror syndrome. Fetuses with Turner syndrome are frequently found to be hydropic on ultrasound. We designed a retrospective multicenter study to evaluate the risk for Mirror syndrome among pregnancies complicated with Turner syndrome and fetal hydrops. Data were extracted from a questionnaire sent to specialists in maternal fetal medicine in Germany. Out of 758 cases, 138 fulfilled our inclusion criteria and were included in the analysis. Of the included 138, 66 presented with persisting hydrops at or after 16 weeks. The frequency of placental hydrops/placentomegaly was rather low (8.1%). Of note, no Mirror syndrome was observed in our study cohort. We propose that the risk of this pregnancy complication varies according to the subjacent cause of fetal hydrops. In Turner syndrome, the risk for Mirror syndrome is lower than that reported in the literature. Our observations are relevant for clinical management and parental counseling.

Determination of paraneoplastic autoimmune responses by tumor cell biology and intratumoral IFN-alpha/IL-12 in breast cancer patients.

A wide variety of cancer types has been associated with paraneoplastic autoimmune disorders and with the induction of autoimmunity against several autoantigens, among them self-antigens that are also expressed by tumor cells. This raises the question of autoimmune disorders as a result of immune reactions to the tumor. To date, however, requirements for the generation of autoimmune reactions in cancer patients remain largely unclear. In this study, we characterized conditions in altogether 131 patients, which determine autoimmune responses in primary breast cancer patients. We used ex vivo IFN-γ EliSpot assays against autologous tumor or skin lysates to evaluate tumor- and auto-reactive T-cells (TCs) in the bone marrow (BM) as well as ELISA, ECLIA, and turbidimetric immunoassays for the detection of auto-reactive antibodies in the peripheral blood and compared results to intratumoral cytokine concentrations and pathobiological features of the primary tumor tissue. We here demonstrate a significant correlation between anti-tumor BMTC responses and cellular autoimmune reactivity in primary breast cancer patients (P = 0.002). Humoral autoimmune reactions, however, were negatively correlated with anti-tumor TC immunity (P = 0.039). We observed auto-reactive BMTCs especially in patients with well-differentiated, hormone receptor-positive carcinomas (P = 0.009). Furthermore, elevated concentrations of intratumoral IFN-α significantly correlated with the induction of cellular autoimmune reactivity (P = 0.0002), while humoral autoimmune reactions correlated with increased levels of intratumoral IL-12 (P = 0.04). Altogether, these data indicate a significant role of the tumor microenvironment and particularly that of IFN-α and IL-12 in the induction of systemic autoimmune responses and imply that the primary tumor tissue represents an integral site of autoimmune regulation in cancer patients.

Is the yolk sac a new marker for chromosomal abnormalities in early pregnancy?

INTRODUCTION: Abnormal yolk sac size is associated with fetal miscarriage. This is a case report of two pregnancies with abnormal yolk sacs. MATERIALS AND METHODS: In one case, a twofold sac was found; in the other case, the yolk sac was not of spherical form. CONCLUSION: Currently available publications demonstrate a correlation between abnormal yolk sac size and miscarriage. However, in both cases a trisomy was confirmed. It should therefore be discussed whether form and size of the yolk sac could be a marker for chromosomal abnormalities of the fetus.

Effects of distant metastasis and peripheral CA 15-3 on the induction of spontaneous T cell responses in breast cancer patients.

Tumor-specific memory T cells are detectable in the bone marrow (BM) of a majority of breast cancer patients. In vitro they can be reactivated to IFN-gamma producing, cytotoxic effector cells and reject autologous, xenotransplanted tumors in NOD/SCID mice after specific restimulation with autologous dendritic cells (DC). In this study, we demonstrate the presence of specific tumor-reactive BM memory T cells in altogether 56 out of 129 primarily operated breast cancer patients by short-term IFN-gamma EliSpot assays with unstimulated T cells and tumor antigen presenting, autologous DCs. We observed tumor-reactive BM memory T cells predominantly in patients with primarily metastatic disease (P = 0.011) or with increased concentrations of tumor marker CA 15-3 in the peripheral blood (P = 0.004), respectively. Memory T cell reactivity against HLA-A(*0201)-restricted peptides from the tumor-associated antigens MUC1, Hpa(16-24) and Hpa(183-191) was also detected particularly in patients with elevated peripheral CA 15-3 concentrations (P < 0.05). Altogether these data indicate that the systemic presence of tumor-derived antigens promotes an induction of tumor-specific cellular immune responses in the human BM.

Quality assured ultrasound simulator training for the detection of fetal malformations.

OBJECTIVE: Sonographic training in obstetrics differs broadly in Germany, although there are clearly defined quality-oriented requirements. In order to improve professional education, a training concept was devised utilizing an ultrasound simulator system. DESIGN: Between October 2004 and May 2006, 100 obstetric ultrasound training courses were held in 12 federal states of Germany. In these daily courses, doctors were trained in the detection of the most common malformations. SAMPLE: One hundred training courses with a total of 1,266 participants. METHODS: As a measure of quality assurance, a standardized questionnaire focusing on testing sonographic proficiency before and after the courses was issued in order to analyze the effect of these simulator-based ultrasound courses. MAIN OUTCOME MEASURES: Effectiveness of the method with reference to its potential role in structured sonographic training. RESULTS: The concept found prevailing approval (90%) at the level of principle, practical implementation, and clinical usefulness. Of the participants, 91% estimated their subjective training effect as good. The questionnaire analysis showed significant improvement. On average, 75.3% of the questions relating to sonographic proficiency were answered correctly at the end of the course as opposed to 48.6% at the beginning. CONCLUSION: Structured ultrasound training courses based on an ultrasound simulator system seem to be useful for defining a basic standardized quality of training and significantly improving examiners' skills. This is a suitable additional instrument to improve the education in obstetric ultrasound.

[Comparison of current methods of prenatal screening for down syndrome]. / Comparación de los métodos actuales de cribado prenatal del síndrome de down.

BACKGROUND: In Spain all pregnant women aged 35 years and older are offered genetic examination through invasive testing in order to detect fetal trisomy 21 cases (maternal age indication (MAI)). In the last decade five distinct software programs utilizing the "first trimester screening (FTS)" were developed. The objective of this study is to compare the test performance of the different screening methods in order to detect the best current approach. METHODS: 7.736 complete first trimester screenings, including the fetal outcome, were realized between 31.08.1999 and 24.05.2007 in three prenatal health centres in Hannover, Peine, and Wolfenbüttel in Germany. Out of these 6.508 cases were analyzed retrospectively in this study. Maternal age was determined and risk calculation with the software programs PIA, PRC, JOY, AFS and AFS-3D was executed. RESULTS: The MAI reached a sensitivity of 57.50%, detecting only 23 out of 40 trisomy 21 cases, and a false positive rate of 21.60%. In comparison, all risk calculation programs obtained superior results, attaining a sensitivity between 90.00% (AFS) and 92.50% (PIA, PRC, JOY, AFS-3D) and a false positive rate between 2.64% (AFS-3D) and 7.87% (PIA). The difference was highly significant (p<0.0001) CONCLUSIONS: The MAI is obsolete and inadequate in comparison with the risk calculation software, out of which all obtained test performances within the range of comparable international publications. Among these programs, JOY, AFS, and AFS-3D obtained the best results.

Improved prenatal aneuploidy screening using the novel advanced first-trimester screening algorithm: a multicenter study of 10,017 pregnancies.

PURPOSE: : It has been postulated that the maternal age component should be completely excluded from first-trimester screening (FTS) for fetal aneuploidies. In this study, we tested a new algorithm known as advanced first-trimester screening (AFS), which disregards maternal age. METHOD: : In a multicenter study, FTS findings were retrieved from 10,017 pregnancies. FTS risk assessment was performed using the Nicolaides method, and the AFS score was calculated. The results of both methods were compared. RESULTS: : Within this population, 81 fetuses had an abnormal karyotype. The sensitivity of the 2 algorithms was 86.4%. When the AFS method was used, the positive predictive value rose from 9.6% (FTS) to 12.4% (AFS). Using AFS, the test positive rate could be decreased by 161 cases (-22.2%) (p < 0.0001), due to a reduction of false positive cases. As a result, the false positive rate of AFS was 24.5% lower than that of FTS, while the same number of aneuploidies was detected. CONCLUSION: : AFS can markedly reduce the rate of false positive test results. If these results are confirmed by larger multicenter studies, the new AFS will represent a great improvement in fetal aneuploidy screening. (c) 2008 Wiley Periodicals, Inc. J Clin Ultrasound, 2008.

Reliability of the microdialysis pump CMA 107 under hyperbaric conditions.

OBJECTIVE: Microdialysis measurements of extracellular substances under hyperbaric conditions were manifold used in several investigations. However, to our knowledge there is no analysis, which verified the applicability of microdialysis pumps under hyperbaric conditions. Thus, a goal of this study was to investigate the reliability of the microdialysis pump (MDP) CMA 107 in a hyperbaric environment up to 2.4bar absolute pressure. METHODS: The CMA 107 with a perfusion rate of 2microL/min was stored in a decompression chamber. The ambient pressure was increased from 1 to 2.4bar absolute within 15min, maintained for 90min and then decreased to 1bar within 15min. The vials were changed every 15min, weighed before as well as after collecting the sample volume and the absolute recovery of glutamate, pyruvate, lactate, glucose and glycerol was determined. The same setup was performed under normobaric conditions. RESULTS: The pumping capacity was 1.7% greater than expected under normobaric conditions, 36.5% less than expected in the compression phase, 10.5% less than expected in the isopression phase and 26.3% greater than expected in the decompression phase under hyperbaric conditions. The absolute recoveries under hyperbaric conditions were affected during the isopression phase with a deviation from -6 to +20% compared to normobaric environments. CONCLUSION: The study demonstrated that an absolute ambient pressure up to 2.4bar did influence the pumping capacity and the reliability of the absolute recovery. These results need to be taken into consideration when interpreting microdialysis studies performed under hyperbaric conditions.

Endothelin-1 and cerebral blood flow in a porcine model.

The purpose of the study was to investigate whether provoked changes of cerebral perfusion pressure and arterial carbon dioxide tension are able to influence the cerebral metabolism of endothelin-1 (ET-1) in a porcine model. Brain tissue oxygen tension, regional cerebral blood flow and mean arterial blood pressure were monitored in 10 healthy pigs during induced hyperventilation (HV), hypertension (HrT) and hypotension (HoT). ET-1 was determined in the arterial and cerebrovenous blood. Microdialysis samples (lactate, glucose and pyruvate) were taken from brain and subcutaneous tissue. A significant decrease (p<0.05) of the arterial ET-1 (1.46+/-0.33 fmol/mL) compared to the baseline (2.18+/-0.36 fmol/mL) was observed after the HoT-period. We detected a positive correlation between cerebrovenous ET-1 and extracellular cerebral glucose (0.68; p<0.05) after the baseline as well as a negative correlation of -0.81 (p<0.005) between the cerebrovenous ET-1 level and the extracellular cerebral lactate after the HoT-period. These data imply that with increasingly pathological changes of the cerebral metabolism endothelin becomes progressively more important in the regulation of cerebral vascular tone.

Maternal anxiety and its correlation with pain experience during chorion villus sampling and amniocentesis.

PURPOSE: Invasive prenatal diagnostic procedures, such as chorion villus sampling (CVS) and amniocentesis (AC), are routinely performed to exclude or diagnose fetal chromosomal abnormalities. The aim of this study was to investigate anxiety-dependent pain experience during CVS and AC and the potential factors that increase anxiety and pain levels. PATIENTS AND METHODS: During a 2-year period, women undergoing invasive procedures in three specialist centers were asked to participate in the study. Anxiety was evaluated before the procedure using the Spielberger State-Trait-Anxiety-Inventory, and pain was evaluated directly after the procedure using a verbal rating scale. RESULTS: Among the women, 348/480 (73%) underwent AC, while 131/480 (27%) underwent CVS. There was a significant correlation between state and trait anxiety (p<0.0001). A positive correlation existed between the degree of anxiety and the level of pain experienced (p=0.01). There was a positive correlation for trait anxiety (p=0.0283) as well as for state anxiety (p=0.0001) and pain perception (p=0.0061) when invasive procedure was performed owing to abnormal ultrasound finding or to a history of fetal aneuploidy. Maternal age was found to be another influencing factor for the experienced pain (p=0.0016). Furthermore, the analysis showed a significant negative correlation between maternal age and anxiety. That applies for trait anxiety (p=0.0001) as well as for state anxiety (p=0.0001). The older the woman, the less anxious the reported feeling was in both groups. The main indication for undergoing CVS was abnormal ultrasound results (45%), and the main reason for undergoing AC was maternal age (58%). CONCLUSION: Procedure-related pain intensity is highly dependent on the degree of anxiety before the invasive procedure. In addition, the indication has a significant impact on the emerging anxiety and consequential pain experiences. These influencing factors should therefore be considered during counseling and performance.

Experiences with continuous intra-arterial blood gas monitoring: precision and drift of a pure optode-system.

OBJECTIVE: The utility of continuous intra-arterial blood gas analysis (CBGA) with combined electrochemical and optode sensors has been demonstrated. More recently, a pure optode sensor with a changed sensing element architecture has become available. The aim was to determine the measurement accuracy and long-term stability of the new sensor. DESIGN: A prospective explorative study was performed. Simultaneous measurements of intermittent blood gas analyses (IBGA) (ABL 610, Radiometer, Copenhagen) and CBGA (Diametrics Medical, High Wycombe, Bucks., UK) were compared using Bland-Altman analysis. PATIENTS: Twenty-five patients admitted to the ICU and requiring mechanical ventilation for an expected minimum of about 96 h were included. RESULTS: Mean monitoring time was 106.1 (range 15-231) hours. Bias and precision for PO(2 )were -0.2 kPa (1%)+/-1.8 kPa (9.5%); PCO(2): 0.03 kPa (0.6%)+/-0.44 kPa (9.3%); pH: -0.001 (0.01%)+/-0.04 (0.45%). The sensor showed no change of measurement characteristics during 4 days of measurement. However, in 69 cases continuous monitoring was interrupted (reversible sudden drops of PO(2) measurement) possibly caused by thrombotic deposition and/or sensor bending and accidental sensor retraction. CONCLUSIONS: The precision and bias of the PCO(2)- and pH-sensing elements were in line with the findings of the older sensor technology. The possibility that the PO(2) optode could offer greater accuracy than the older technology is suggested by comparisons with results reported in previous studies. No sensor drift occurred during long-term measurement over more than 4 days.