Detection of bacterial contamination in platelet concentrates by a sensitive flow cytometric assay (BactiFlow): a multicentre validation study.

BACKGROUND: Bacterial contamination of platelet concentrates (PCs) still represents an ongoing risk. As a result of septic complications, particularly observed with older PCs, the shelf life of PCs has been reduced in Germany to 4 days. In this study, bacterial screening of PCs by BactiFlow (BF) flow cytometry was introduced in three German blood services to evaluate the robustness and applicability of the assay. Results were used to discuss the potential for the extension of PC shelf life to 5 days. STUDY DESIGN AND METHODS: A total of 1956 PCs were tested on days 4 or 5+ after PC production using the BF, whereas the BacT/Alert culture system served as reference method. RESULTS: Two PCs were confirmed positive by culture only and were identified as Propionibacterium acnes and Staphylococcus species. Two PCs were confirmed positive for Streptococcus mitis by BF and culture. Additionally, two PCs were culture-positive only in one culture bottle (aerobic: S. mitis and anaerobic: S. hominis). Retrospective analysis of bacterial growth kinetics provide the indication that corresponding bacterial titres were most likely below the BF analytical detection limit (<150 CFU mL(-1) ) and had probably no transfusion relevance. All remaining specimens were tested negative. CONCLUSIONS: Testing of PCs by BF was successfully implemented. The BF proved sufficient as a rapid screening method to improve PC safety. This study further provides data supporting the extension of PC shelf life to 5 days after negative BF testing on day 4.

Autologous stem cell therapy in the treatment of limb ischaemia induced chronic tissue ulcers of diabetic foot patients.

BACKGROUND AND AIM: Despite improvements in surgical revascularisation, limitations like anatomical factors or atherosclerosis limit the success of revascularisation in diabetic patients with critical limb ischaemia. Stem cells were shown to improve microcirculation in published studies. The aim of this study was to evaluate safety, feasibility and efficacy of transplantation of bone marrow derived cellular products regarding improvement in microcirculation and lowering of amputation rate. METHODS: Bone marrow mononuclear cells (BMCs) in comparison with expanded bone marrow cells enriched in CD90+ cells ('tissue repair cells', TRCs) were used in the treatment of diabetic ulcers to induce revascularisation. Diabetic foot patients with critical limb ischaemia without option for surgical or interventional revascularisation were eligible. Parameters examined were ABI, TcPO(2) , reactive hyperaemia and angiographic imaging before and after therapy. RESULTS: Of 30 patients included in this trial, 24 were randomised to receive either BMCs or TRCs. The high number of drop-outs in the control group (4 of 6) led to exclusion from evaluation. A total of 22 patients entered treatment; one patient in the TRC group and two in the BMC group did not show wound healing during follow up, one patient in each treatment group died before reaching the end of the study; one after having achieved wound healing (BMC group), the other one without having achieved wound healing (TRC group). Thus, 18 patients showed wound healing after 45 weeks. The total number of applicated cells was 3.8 times lower in the TRC group, but TRC patients received significantly higher amounts of CD90+ cells. Improvement in microvascularisation was detected in some, but not all patients by angiography, TcPO(2) improved significantly compared with baseline in both therapy groups. CONCLUSION: The transplantation of BMCs as well as TRCs proved to be safe and feasible. Improvements of microcirculation and complete wound healing were observed in the transplant groups.

Bacterial screening by flow cytometry offers potential for extension of platelet storage: results of 14 months of active surveillance.

BACKGROUND: Bacterial contamination is currently the major infectious hazard of platelet transfusion in developed countries. It has been demonstrated that a significant transfusion risk remains, in particular with older platelet concentrates (PCs). In 2009, the shelf life of PCs was therefore reduced in Germany to 4 days after the day of production according to Vote 38. The aim of the present study was the application and implementation of a recently developed flow cytometry-based rapid screening method (BactiFlow) for bacterial contamination at the end of PC shelf life as a routine in-process control. STUDY DESIGN AND METHODS: A total of 472 apheresis-derived PCs were tested using the BactiFlow flow cytometric assay to detect and count bacteria based on esterase activity in viable bacterial cells, while the BacT/Alert automated culture system served as the reference method. The automation potential of the flow cytometric assay was analysed by applying the semi-automated BactiFlow ALS system. RESULTS: An algorithm was developed for use in routine blood bank operations to extend the storage period of PCs. Two of the 472 apheresis PCs tested were positive in culture and identified as Propionibacterium species. One PC was positive for Staphylococcus aureus by both methods. All remaining specimens were tested negative by both methods. CONCLUSIONS: Our study demonstrates that routine bacterial testing of PCs was successfully implemented and the established algorithm proved efficient. The BactiFlow flow cytometric assay is the first rapid screening method which is suitable for a routine application combined with a high sensitivity.

Differentiation of species of the Streptococcus bovis/equinus-complex by MALDI-TOF Mass Spectrometry in comparison to sodA sequence analyses.

The Streptococcus bovis/equinus complex is a heterogeneous group within the group D streptococci with important clinical relevance regarding infective endocarditis, sepsis and colon carcinoma. The taxonomic identification of species and sub-species of this complex, by the standard methods remains difficult. In the present study, we compared the cluster analysis of 88 strains of species of the S. bovis/equinus complex by sequence analysis of the manganese-dependent superoxide dismutase gene (sodA) and by Matrix Assisted Laser Desorption/Ionization-Time Of Flight Mass Spectrometry (MALDI-TOF MS). We observed a high congruence of strain grouping by MALDI-TOF MS in comparison with sodA sequence analyses, demonstrating the accuracy and reliability of MALDI-TOF MS in comparison to DNA sequence-based method. By generating mass spectra for each species and sub-species, we were able to discriminate all members of the S. bovis/equinus complex. Furthermore, we demonstrated reliable identifications to the species level by MALDI-TOF MS, independently of cultivation conditions.

Diffusion-weighted magnetic resonance imaging for the detection of ischemic brain lesions in coronary artery bypass graft surgery: relation to extracorporeal circulation and heparinization.

AIM: Cognitive decline is a well recognized complication after on-pump coronary artery bypass graft (CABG) surgery. We investigated whether the design of extracorporeal circulation (ECC) and the extent of perioperative heparinization have an impact on neurological dysfunction. METHODS: Sixty-three CABG surgery patients were randomly perfused with an uncoated ECC-set (group A) or with two different heparin-coated ECC-sets (groups B and C). In groups A and B, systemic heparin was given in doses of 400 IU/kg body weight, whereas group C received 150 IU/kg body weight. ECC sets in group C included a diagonal pump and low priming as opposed to roller pumps in groups A and B. Furthermore, in group C blood contact to surfaces other than endothelium and heparin coated material was eliminated. Brain lesions were detected by diffusion-weighted magnetic resonance imaging (DWI). Neurological complications were assessed clinically until discharge (manifest motoric, sensitive or cognitive disturbance). Biochemical coagulation and inflammation parameters were measured pre-, peri-, and postoperatively. RESULTS: No major neurological events were observed in either group until discharge. DWIs showed 61 new lesions in 19 of 45 patients who terminated all MRI study procedures. Number and volume of the lesions did not differ between groups (P>0.05). Biochemical and inflammatory parameters showed the expected time courses and variations between groups. CONCLUSION: Ischemic brain lesions are frequently observed in CABG surgery patients but are neither associated with clinically relevant neurological complications nor with ECC set-up and intraoperative heparin dosage. DWI may help in the development of new surgical strategies to reduce postoperative brain damage.

Preoperative haemostasis testing does not predict requirement of blood products in cardiac surgery.

OBJECTIVE: Standard haemostasis screening tests are performed to reveal unknown congenital or acquired disturbances of plasma and/or platelet haemostasis. Since their diagnostic efficacy is often low, routinely performed haemostasis testing has been questioned. We investigated whether preoperatively assessed haemostasis testing can be used to predict the requirement of blood products. METHODS: We retrospectively assessed haemostasis parameters including platelet function testing by PFA 100 as well as the numbers of red blood cell (RBC) concentrates, fresh frozen plasmas (FFPs), and platelet concentrates (PCs) that were given peri-operatively and during the first two postoperative days in 2,831 cardiac surgery patients. Logistic regression analyses were used to select those parameters, which could predict blood product requirement. RESULTS: Of our study cohort, 56.5% needed RBCs, 15% FFPs, and 5% PCs. The need for RBCs was associated with significantly altered pre-operative values of most haemostasis parameters. However, by the use of logistic regression analysis fibrinogen was the only haemostasis parameter that was independently associated with the use of RBCs (odds ratio 1.56; 95% CI: 1.27-1.91; P <0.001). The predictive value of other parameters such as age, body weight, haemoglobin, and haematocrit was however much higher in comparison to fibrinogen (odds ratios: 1.92-3.50; P <0.001). It was not possible to develop a score based on haemostasis parameters to accurately identify patients at risk for RBC use. Moreover, we were unable to estimate the need for FFPs and PCs using preoperative haemostasis testing. CONCLUSIONS: Our data demonstrate that preoperatively performed haemostasis testing is not predictive in estimating the need for blood products in cardiac surgery patients.

Leptin decreases postprandially in people with type 2 diabetes, an effect reduced by the cooking method.

Leptin modulates satiety and increases in obesity and type 2 diabetes mellitus in parallel with leptin resistance. Postprandial leptin regulation has been previously postulated to depend on meal composition, but data are controversial. The hypothesis of our study was that in people with type 2 diabetes mellitus, a postprandial leptin regulation exists that can be regulated not only by meal composition but also by the cooking method. In 20 inpatients with type 2 diabetes (mean age: 55.9 years), the acute effects of 2 meals, a high-heat-processed meal HHPM or a low-heat-processed meal LHPM, on leptin levels were studied on 2 different days in a randomized, crossover design. Both test meals had similar ingredients and differed only in the cooking method used. Parameters were measured after an overnight fast and at 2, 4, and 6 h postprandially. The HHPM induced a marked decrease in leptin levels, from 8 717+/-2 079 pg/ml at baseline to 6 788+/-1 598 pg/ml at 2 h postprandially (-1 929 pg/ml, -22%*), an effect significantly reduced by the LHPM, where values were 8 563+/-1 900 pg/ml at baseline and 7 425+/-1 591 pg/ml at 2 h postprandially (-1 138 pg/ml, -13%* (double dagger)) (*p<0.05 vs. baseline, (double dagger)p<0.05 vs. HHPM). Parameters of oxidative stress and blood AGEs increased only following the HHPM, while postprandial glucose, triglycerides, and insulin excursions were similar between meals. Postprandial leptin decreases following a HHPM meal in people with T2DM, an effect reduced by the cooking method.

[A telemetrically-guided program for weight reduction in overweight subjects (the SMART study)]. / Telemedizinisch betreutes Programm zur Gewichtsreduktion bei Ubergewichtigen (SMART-Studie).

BACKGROUND AND OBJECTIVE: Compliance with weight reducing programs can be improved by intensive care and control. We tested a telemetrically-guided weight reduction program in overweight and obese persons. PATIENTS AND METHODS: 200 outpatients (62 males) with a mean body mass index of 34 kg/m (2) and a mean age of 47 years participated in a prospective study for one year. During the first six months, telemetrical support (weight-transmission via Bluetooth (short range)-technology, 20-minutes telephone consultation with a nutritionist) was given weekly. After six months, participants were randomly assigned either to a group with further telemonitoring support (telemetric group) or to a group without contact to our clinic (control group). At baseline, and after six and twelve months, body weight, body composition (bioelectrical impedance analysis), and parameters of the metabolic syndrome were assessed at our clinic. RESULTS: 16 participants terminated the study prematurely during the first 6 months and 19 participants (10 from the telemetric group and 9 from the control group) during the second 6 months. According to the intention-to-treat principle, mean weight loss was 6.7 kg (p < 0,001), mean loss of body fat was 5.1 kg (p < 0,001), and mean loss of fat-free mass was 1.6 kg (p < 0,001) within the first six months. Moreover, metabolic and cardiovascular risk markers such as waist circumference, blood pressure, serum triglycerides and blood glucose declined significantly (p < 0,001). Prevalence of the metabolic syndrome fell from 49.5% to 42.0 % (p < 0,05). During the second six months body fat content, waist circumference, and blood glucose increased again in the control group but not in the telemetric group (p < 0,05-0,001). CONCLUSION: The telemetrically-guided weight loss program was a more efficacious measure than the less intensive support without telemonitoring.

Heparin-coated extracorporeal circulation in combination with low dose systemic heparinization reduces early postoperative blood loss in cardiac surgery.

AIM: According to a recently performed meta-analysis, heparin-bonded circuits do not reduce blood loss in cardiac surgery patients compared to nonheparin-bonded circuits within the first 24 h postoperatively. We investigated the effects of heparin-coated circuits in combination with a reduced systemic heparin dose on early postoperative blood loss (first 12 h), platelet function, and postoperative complications. METHODS: Patients who underwent their first coronary artery bypass graft surgery were included in a randomized prospective study. Group A (n=149) was perfused with an uncoated extracorporeal circulation (ECC)-set and groups B (n=152) and C (n=149) with heparin-coated ECC-sets. In groups A and B, conventional dose systemic heparin was given, whereas group C received low dose systemic heparin. Blood loss was assessed within the first 12 h postoperatively. Moreover, biochemical parameters of pro-coagulant activity and immunological function were measured. RESULTS: None of the pro-coagulant activity markers and immunological parameters measured differed preoperatively or postoperatively between study groups. However, intraoperative platelet counts and maximal intraoperative concentrations of platelet factor 4, ss-thromboglobulin, and poly-morpho-nuclear (PMN)-elastase were lowest in group C, whereas group C also had the highest concentrations of thrombin-antithrombin complex (P<0.018-0.001). Blood loss within the first 12 h postoperatively was 457 +/- 204 mL in group A, 431 +/- 178 mL in group B, and 382 +/- 188 mL in group C (P<0.01). Complication rates and 30-day mortality did not differ between study groups. CONCLUSION: The combined use of heparin-coated circuits and low dose systemic heparinization is able to reduce early postoperative blood loss without enhancing the risk of complications.

Spore-forming organisms in platelet concentrates: a challenge in transfusion bacterial safety.

Bacterial detection and pathogen reduction are widely used methods of minimizing the risk of transfusion-transmitted bacterial infection. But, bacterial spores are highly resistant to chemical and physical agents. In this study, we assessed the bacterial proliferation of spore-forming organisms seeded into platelet concentrates (PCs) to demonstrate that spores can enter the vegetative state in PCs during storage. In the in vitro study, PCs were inoculated with 1-10 spores mL(-1)of Bacillus cereus (n = 1), Bacillus subtilis (n = 2) and Clostridium sporogenes (n = 2). Sampling was performed during 6-day aerobic storage at 22 degrees C. The presence of bacteria was assessed by plating culture, automated culture and real-time reverse transcriptase-polymerase chain reaction (RT-PCR). Spores of the C. sporogenes do not enter the vegetative phase under PC storage conditions, whereas B. subtilis and B. cereus showed growth in the PC and could be detected using RT-PCR and automated culture. Depending on the species and inoculums, bacterial spores may enter the vegetative phase during PC storage and can be detected by bacterial detection methods.

Sterility screening of platelet concentrates: questioning the optimal test strategy.

BACKGROUND: Routine bacterial monitoring of apheresis platelet concentrates (APC) and pooled platelet concentrates (PPC) was introduced in two German blood services using culture and real-time reverse transcriptase (RT)-polymerase chain reaction (PCR). The results of testing are reviewed and used to discuss different strategies for detection of bacterial contamination of PCs. STUDY DESIGN AND METHODS: Two thousand three hundred and sixty-two APCs and 1993 PPCs have been tested by real-time RT-PCR and the BacT/Alert automated culturing system using aerobic and anaerobic culture bottles. After standard processing of PCs and storage of 22-24 h at 20-24 degrees C with agitation, samples were taken under aseptic conditions. Reactive culture bottles were confirmed as positive and bacterial isolates were identified by 16S rRNA analysis and biochemical tests. RESULTS: Seventeen of 2362 tested APCs were reactive in culture and one also in RT-PCR. Of these, 13 APCs were identified as initially positive as Staphylococcus warneri (n = 1, positive in aerobic and anaerobic culture), Propionibacterium acnes (n = 12, positive only in anaerobic culture) and four were initially reactive. Two of 1993 PPCs were initially reactive (anaerobic) and two more were confirmed positive (anaerobic) from a repeat culture and identified as P. acnes. All remaining specimens were tested negative. CONCLUSION: Our study demonstrates that the predominant organisms implicated in platelet bacterial contamination are part of the human skin flora. Inoculating blood culture systems and anaerobic cultivation detects these bacteria after approximately 3-7 days when blood products have been transfused. Based on the presented data different screening strategies are discussed.

Propionibacterium acnes lacks the capability to proliferate in platelet concentrates.

BACKGROUND AND OBJECTIVES: Propionibacterium acnes is considered to be one of the most frequent contaminants of platelet concentrates (PCs) when anaerobic culture-based detection methods are used. But Propionibacteria are often detected too late when blood products have already been transfused. Therefore, its transfusion relevance is still demanding clarification because studies of the outcome of patients transfused with P. acnes-contaminated PCs are still uncommon. In this study, we monitored clinical effects in patients after transfusion of PCs, which were detected too late in sterility testing. Furthermore, we assessed the bacterial proliferation of Propionibacterium species seeded into PCs to clarify their significance for platelet bacteria screening. MATERIALS AND METHODS: In the look-back process, we followed the route of the putative contaminated PC units from storage to transfusion. In the in vitro study, PCs were inoculated with 1-100 colony-forming unit (CFU)/ml of clinical isolates of Propionibacteria (n = 10). Sampling was performed during 10-day aerobic storage at 22 degrees C. The presence of bacteria was assessed by plating culture and automated BacT/Alert culture system. RESULTS: Propionibacterium acnes shows slow or no growth under PC storage conditions. Clinical signs of adverse events after transfusion of potentially contaminated PC units were not reported. CONCLUSION: Propionibacteria do not proliferate under PC storage conditions and therefore may be missed or detected too late when blood products have already been transfused.

Human xylosyltransferases in health and disease.

The xylosyltransferases I and II (XT-I, XT-II, EC 2.4.2.26) catalyze the transfer of xylose from UDP-xylose to selected serine residues in the proteoglycan core protein, which is the initial and ratelimiting step in glycosaminoglycan biosynthesis. Both xylosyltransferases are Golgi-resident enzymes and transfer xylose to similar core proteins acceptors. XT-I and XT-II are differentially expressed in cell types and tissues, although the reason for the existence of two xylosyltransferase isoforms in all higher organisms remains elusive. Serum xylosyltransferase activity was found to be a biochemical marker for the assessment of disease activity in systemic sclerosis and for the diagnosis of fibrotic remodeling processes. Furthermore, sequence variations in the XT-I and XT-II coding genes were identified as risk factors for diabetic nephropathy, osteoarthritis or pseudoxanthoma elasticum. These findings point to the important role of the xylosyltransferases as disease modifiers in pathologies which are characterized by an altered proteoglycan metabolism. The present review discusses recent advances in mammalian xylosyltransferases and the impact of xylosyltransferases in proteoglycan-associated diseases.

Wound therapy with autologous bone marrow stem cells in diabetic patients with ischaemia-induced tissue ulcers affecting the lower limbs.

Previous studies suggest that autologous transplantation of bone marrow mononuclear cells is safe and effective in inducing therapeutic angiogenesis in patients with peripheral arterial occlusive disease (PAOD). Here we discuss a multidisciplinary approach to treating PAOD with a focus on the use of angiological diagnostic tools. We conclude that our autologous stem cell therapy is working in this patient and it is a potential new therapeutic option for diabetic patients with chronic foot ulcers induced by critical limb ischaemia.

Detection of bacteria in platelet concentrates prepared from spiked single donations using cultural and molecular genetic methods.

Bacteria show differences in their growth kinetics depending on the type of blood component. On to storage at 22 degrees C, platelet concentrates (PCs) seem to be more prone to bacterial multiplication than red cell concentrates. Knowledge of the potential for bacterial proliferation in blood components, which are stored at a range of temperatures, is essential before considering implementation of a detection strategy. The efficacy of bacterial detection was determined, using real-time reverse transcriptase-polymerase chain reaction (RT-PCR), following bacterial growth in blood components obtained from a deliberately contaminated whole-blood (WB) unit. Cultivation was used as the reference method. WB was spiked with 2 colony-forming units mL(-1)Staphylococcus epidermidis or Klebsiella pneumoniae, kept for 15 h at room temperature and component preparation was processed. Samples were drawn, at intervals throughout the whole separation process, from each blood component. Nucleic acids were extracted using an automated high-volume extraction method. The 15-h storage revealed an insignificant increase in bacterial titre. No bacterial growth was detected in red blood cell or plasma units. K. pneumoniae showed rapid growth in the pooled PC and could be detected immediately after preparation using RT-PCR. S. epidermidis grew slowly and was detected 24 h after separation. These experiments show that sampling is indicative at 24 h after preparation of PCs at the earliest to minimize the sampling error.

Novel sequence variants in the human xylosyltransferase I gene and their role in diabetic nephropathy.

AIMS: Decreased content of heparan sulphate proteoglycans (HSPGs) is a characteristic of the glomerular basement membrane (GBM) in diabetes and contributes to the development of diabetic nephropathy (DN). Xylosyltransferase I (XT-I) is the chain-initiating enzyme involved in the biosynthesis of HSPGs. This study investigated a possible association between XYLT-I sequence variants and susceptibility to DN. METHODS: Screening of all XYLT-I exons was performed in 74 caucasians with Type 1 diabetes (48 with and 26 without DN) and in 13 non-diabetic control subjects using denaturing high-performance liquid chromatography. RESULTS: Fifteen XYLT-I sequence variants were identified. Of these, six were previously unknown. There were significant differences in the allele frequencies of the three polymorphisms (c.343G-->T (p.A115S), IVS3+10C-->T, IVS3+30G-->C) in Type 1 diabetic patients and healthy controls. CONCLUSIONS: The occurrence of DN is independent of the XYLT-I variants detected in our study. However, three XYLT-I polymorphisms may be linked to Type 1 diabetes. Since we have previously proposed that one of these polymorphisms was not associated with Type 1 diabetes (Schön S et al. Kidney Int 2005; 68: 1483-1490), larger-scale analysis is clearly necessary to pinpoint the significance of this mutation.

Polymorphisms in the xylosyltransferase genes cause higher serum XT-I activity in patients with pseudoxanthoma elasticum (PXE) and are involved in a severe disease course.

BACKGROUND: Pseudoxanthoma elasticum (PXE) is a heritable connective tissue disorder caused by mutations in the ABCC6 gene. Fragmentation of elastic fibres and deposition of proteoglycans result in a highly variable clinical picture. The altered proteoglycan metabolism suggests that enzymes from this pathway function as genetic co-factors in the severity of PXE. Therefore, we propose the XYLT genes encoding xylosyltransferase I (XT-I) as the chain-initiating enzyme in the biosynthesis of proteoglycans and the highly homologous XT-II as potential candidate genes. METHODS: We screened all XYLT exons in 65 German PXE patients using denaturing high performance liquid chromatography and analysed the influence of the variations on clinical characteristics. RESULTS: We identified 22 variations in the XYLT genes. The missense variation p.A115S (XT-I) is associated with higher serum XT activity (p = 0.005). The amino acid substitution p.T801R (XT-II; c.2402C>G) occurs with significantly higher frequency in patients under 30 years of age at diagnosis (43% v 26%; p = 0.04); all PXE patients with this variation suffer from skin lesions compared to only 75% of the wild type patients (p = 0.002). c.166G>A, c.1569C>T, and c.2402C>G in the XYLT-II gene were found to be more frequent in patients with higher organ involvement (p = 0.04, p = 0.01, and p = 0.02, respectively). CONCLUSIONS: Here we show for the first time that variations in the XYLT-II gene are genetic co-factors in the severity of PXE. Furthermore, the higher XT activity in patients with the exchange p.A115S (XT-I) indicates that this polymorphism is a potential marker for increased remodelling of the extracellular matrix.

Mutational and functional analyses of xylosyltransferases and their implication in osteoarthritis.

OBJECTIVE: The hallmark in osteoarthritis (OA) is the loss of proteoglycans (PGs) in articular cartilage (AC). Xylosyltransferase I (XT-I) catalyzes the transfer of xylose to serine residues in the core protein and initiates the biosynthesis of PGs in AC. The XYLT-II gene encodes a highly homologous protein but its biological function is not yet known. Here we investigate for the first time genetic variations in the XYLT-genes and serum XT-I activities and their implication in OA. METHODS: Denaturing high-performance liquid chromatography (DHPLC) was used for the screening of the XYLT-genes in 49 OA patients. For a detailed characterization of XT-I amino acid exchanges we performed recombinant expression of XT-I mutants in insect cells. Furthermore, the XT activity was measured in the patients' serum. RESULTS: The variation c.1569C>T (XYLT-II) occurs with a significantly higher frequency in younger OA patients in comparison with the older ones (P<0.001) and the controls (P<0.02). Furthermore, significantly higher serum XT activities were found in patients with a long disease duration of OA (P<0.04). The recombinant XT-I mutants p.P385L and p.I552S had reduced enzymatic activity (85% and 74%) compared with the wildtype (wt). CONCLUSIONS: Our findings indicate a correlation of the c.1569 T-allele in XYLT-II with an earlier manifestation of OA and that the serum XT activity is a potential biochemical marker for staging and monitoring the progression of AC damage in OA. Comparison of XT-I activity in mutant enzymes in vivo and in vitro revealed that heterozygous mutations are not involved in OA.