Mid-term survivorship of fixed bearing unicondylar knee arthroplasty with no exclusion of early PFJ arthritis or ACL deficiency: Analysis of clinical and radiological predictors.

PURPOSE: Fixed bearing (FB) UKA constituted 63.7% of unicondylar knee arthroplasties in 2020 Australian Registry with the longest UKA survivorship. The significance of patellofemoral joint (PFJ) arthritis, ACL deficiency, post-operative anteromedial pain, radiosclerosis or radiolucency on survivorship of FB UKA is not established. The aim of this study was to analyze the medium-term survivorship of fixed-bearing UKA with no exclusion of PFJ OA and ACL deficiency. Predictors for failure were analyzed. METHODS: FB UKA performed in 2011-17 were reviewed. Cases with PFJ OA or ACL deficiency were not excluded. The effect on survivorship by ACL deficiency, PFJ arthritis, post-operative anteromedial pain and radiological abnormalities were analyzed. RESULTS: There were 96 UKA with follow-up time of 66 ± 18 months (27-98). The mean age was 70 ± 9 years, BMI 25.8 ± 2.6 kg/m2. Alignment was varus 9° ± 4° pre-operatively and varus 3° ± 3° post-operatively. There were four revisions (4.2%) and 4 deaths (4.2%). Reasons for revisions were loosening (n = 1), persistent pain (n = 2) and lateral compartment disease (n = 1). Estimated survival at 8.3 years was 94.7% (95% CI 91.6-97.7). BMI ≥30 was found to be a significant predictor for failure. The incidence of radiographic abnormalities was 75% for PFJ arthritis, 39% for tibial tray overhang, 14% for radiolucency or radiosclerosis, 5% for ACL deficiency and 5% for edge loading respectively but they were not significantly associated with lower survivorship or anteromedial knee pain. The presence of anteromedial pain after surgery in 36.5% was also not significantly associated with survivorship. CONCLUSION: FB UKA with no exclusion of early PFJ arthritis and ACL deficiency has satisfactory medium-term survivorship. BMI ≥30 could have higher risk of all-cause revision. Tibial tray overhang, non-progressive radiolucency or radiosclerosis do not seem to be associated with anteromedial knee pain or poorer medium term survivorship.

Invasive Burkholderia cepacia Complex Infections among Persons Who Inject Drugs, Hong Kong, China, 2016-2019.

During March 2016-January 2019, Burkholderia cepacia complex (BCC) infection developed in 13 persons who inject drugs (PWID) in Kowloon West Region, Hong Kong, China. Seven cases were infective spondylitis, 2 endocarditis, 2 septic arthritis, 1 intramuscular abscess and bacteremia, and 1 necrotizing fasciitis. Pulsed-field gel electrophoresis revealed that the isolates from 9 patients were clonally related. This clone caused major illness, and 11 of the 13 patients required surgical treatment. Clinicians should be aware of this pathogen and the appropriate broad-spectrum antimicrobial drugs to empirically prescribe for PWID with this life-threatening infection. Close collaboration among public health authorities, outreach social workers, and methadone clinics is essential for timely prevention and control of outbreaks in the PWID population.

Proximal tibial bone loss in the first 2 years after unicondylar knee arthroplasty: Anatomical pattern, predictors and clinical correlation.

BACKGROUND: Tibial stress fracture, anteromedial bone pain, and early subsidence could occur after unicondylar knee arthroplasty (UKA). The change in metaphyseal tibial bone density (MTBD) in the coronal and sagittal planes after UKA might be a contributing factor, but this has rarely been investigated. The aim of this study was to assess the regional and temporal change in MTBD in the coronal and sagittal planes in the first 2 years after UKA. METHODS: Patients with fixed-bearing medial UKA were recruited. The change in MTBD in the first 24 months after UKA using digital radiological densitometry (DRD) was measured. Potential predictors and clinical correlations were analyzed. RESULTS: Eighty-four cases (female 60%) were selected for review. The follow up time was 63 (±17) months. Anterior and medial regions had the largest proportion of cases with MTBD reduction (90-97%, P < 0.05). Reduction was largest at anterior and medial regions (21-29%, P < 0.05) and smallest at posterior and lateral regions (5-15%, P < 0.05). Maximal reduction occurred at 12 months for the medial region and 24 months for the anterior region. MTBDs of both regions were not significantly influenced by any confounding factors. Significant correlation was found between medial MTBD and Function Score at 6 months. CONCLUSIONS: Bone loss in a zonal pattern occurs in the first 2 years after UKA with the largest loss in the anterior region below the tibial tray. It is not affected by body mass index, perioperative alignment, or angle of correction. This suggests a physiological response to trauma other than a mechanical response to the change in bone strain.

Machine learning application for the prediction of SARS-CoV-2 infection using blood tests and chest radiograph.

Triaging and prioritising patients for RT-PCR test had been essential in the management of COVID-19 in resource-scarce countries. In this study, we applied machine learning (ML) to the task of detection of SARS-CoV-2 infection using basic laboratory markers. We performed the statistical analysis and trained an ML model on a retrospective cohort of 5148 patients from 24 hospitals in Hong Kong to classify COVID-19 and other aetiology of pneumonia. We validated the model on three temporal validation sets from different waves of infection in Hong Kong. For predicting SARS-CoV-2 infection, the ML model achieved high AUCs and specificity but low sensitivity in all three validation sets (AUC: 89.9-95.8%; Sensitivity: 55.5-77.8%; Specificity: 91.5-98.3%). When used in adjunction with radiologist interpretations of chest radiographs, the sensitivity was over 90% while keeping moderate specificity. Our study showed that machine learning model based on readily available laboratory markers could achieve high accuracy in predicting SARS-CoV-2 infection.

Who are less likely to return to work after getting injured on duty? A 12-month epidemiological evaluation in an orthopedic and traumatology center in Hong Kong.

OBJECTIVES: Cases of injury on duty (IOD) are common in Hong Kong, but literature on this group of patients is limited. This study aims to describe local IOD cases' epidemiological characteristics and identify factors affecting return to work (RTW) outcomes. METHODS: This is a retrospective epidemiological study of IOD patients in the orthopedic and traumatology center of Yan Chai Hospital in 2016, using the hospital's electronic clinical record analysis and reporting system; 323 out of the 10 730 patients (M:F = 206:117; mean age 46.9 ± 11.3) were included. Data on demographics, the injury episode, administrative procedures, treatment and rehabilitation were collected. Outcomes were measured by "RTW" and "time to RTW from injury." RESULTS: Around 80% of patients had a successful RTW and the mean time to RTW was 10.6 ± 9.0 months. Patients who were female, divorced or widowed and living alone in a public rental flat were less likely to RTW. Psychiatric consultations (OR 13.70, P < .001), legal disputes (OR 8.20, P < .001) and more than 5 months of waiting time for physiotherapy (OR 3.89, P = .002) were the strongest among the numerous risk factors for non-RTW. An increase in one visit to the general outpatient clinic and the presence of legal disputes had lengthened the time to RTW by 4.8 days (P < .001) and 18.0 months (P < .001), respectively. CONCLUSIONS: Several demographic, psychosocial and administrative factors were negatively associated with RTW in the local population. Recommendations were made for healthcare providers and policymakers accordingly.

Forgotten Joint Score for early outcome assessment after total knee arthroplasty: Is it really useful?

BACKGROUND: Forgotten Joint Score (FJS) has become a popular tool for total knee arthroplasty (TKA), but almost all studies had assessment performed 1 year after surgery. There is a need for a sensitive tool for earlier outcome assessment. The aim of this study was to investigate the usefulness of FJS within the first year after TKA. METHODS: This was a cross-sectional study. Patients within the first year after primary TKA were recruited. FJS was translated into the local language with a cross-cultural adaptation and was validated by assessing the correlation with the Western Ontario and McMaster Universities Arthritis Index score (WOMAC). Ceiling and floor effects (highest or lowest 10% or 15%) of both scores were compared. Skewness of scores was assessed with a histogram. RESULTS: One hundred sixty-three subjects were recruited: 84 (51.5%) had evaluation at 3 months after the operation, 56 (34.4%) at 6 months, and 23 (14.1%) at 12 months. FJS had fewer patients at the highest 10% (10.7% vs. 16.1%, P = 0.046) or 15% (19.6% vs. 32.1%, P = 0.027) at 6 months and within the first year overall (6.7% vs. 13.5%, P <0.001; 14.1% vs. 22.7%, P <0.001). Also, it had more patients at the lowest 10% (16.7% vs. 0%, P <0.001) or 15% (21.4% vs. 0%, P <0.001) at 3 months, 6 months (10.7% vs. 0%, P <0.001), and overall (12.9% vs. 0%, P <0.001; 16.6% vs. 0%, P <0.001). The skewness was much less than WOMAC (0.09 vs. -0.56). CONCLUSIONS: FJS has a low ceiling effect but a high floor effect in the first year after TKA. Such characteristics make it less useful for the general assessment of early patient report outcome after operation.

Intraoperative femoral condyle fracture in primary total knee arthroplasty - a case-control study in Asian population.

PURPOSE: Intraoperative femoral condyle fracture is a significant but rarely reported complication during primary total knee arthroplasty (TKA). This is the first study to identify the incidence, risk factors, location and outcome of these fractures in an Asian population with modern posterior-stabilized (PS) TKA. MATERIALS AND METHODS: We reviewed 2682 consecutive primary TKAs performed between 2011 and 2017 in a single centre; 23 femoral condyle fractures were identified and analysed. RESULTS: Fractures were managed conservatively with screw fixation or revision arthroplasty. Mean follow up was 3.0 years (range 3 months to 5.9 years). All patients achieved bone union and good functional outcome. The mean Knee Society Knee score was 89.4 (range 71-100) and the function score was 80.2 (range 60-95) at a mean of 3.0 years post-operation. Bilateral surgery was found to be a significant risk factor for femoral condyle fracture, while there was a higher trend of fracture in female patients and Stryker articular surface mounted (ASM) navigation. CONCLUSIONS: Intraoperative fracture is not uncommon with modern PS TKA. Postulated risk factors for fracture were discussed. Early identification of risk factors and a rigorous surgical technique may reduce risk of fracture. A good functional result was expected after proper treatment.

No difference in patient preference for medial pivot versus posterior-stabilized design in staged bilateral total knee arthroplasty: a prospective study.

PURPOSE: Medial pivot (MP) TKA has been shown to mimic normal knee kinematics with long-term survivorship comparable to most contemporary TKA. However, there are inadequate evidences to suggest its superiority in terms of patient preference and satisfaction. The aim of this study is to compare the MP with posterior-stabilized (PS) TKA in terms of patient preference and satisfaction. METHODS: 46 patients with staged bilateral TKA were recruited. TKA with MP or PS design was performed at interval of 6-12 months. Patient preference, patient satisfaction score (0-100), Forgotten Joint Score (FJS), range of motion (ROM), Pain Score, Knee Society Score (KSS), Knee Function Score (KFS) and WOMAC Score were compared at up to 12 months. RESULTS: The mean age was 70 and 69.6% were female. There was no difference in all preoperative parameters, operative time and length of stay between two knees. No difference was found in in range of motion and all outcome scores at 6 months and 12 months. Satisfaction score was similar for the two designs (82 vs 85, p = n.s.) at 1 year after the second TKA. Proportion of patients with preference on one design over another was not significantly different (28.9 vs 35.6%, p = n.s.). CONCLUSIONS: There is no evidence to support the superiority of MP TKA over PS TKA in terms of preference and satisfaction. The choice between MP TKA versus PS TKA maybe more a surgeon's preference than a patient's preference based on current evidence.

Tibial tray thickness does not significantly increase medial tibial bone resorption: Using tibial bone density as an objective measurement method.

BACKGROUND: Recent studies have reported the occurrence of medial tibial bone resorption following total knee replacement. One study proposed that a thick tibial tray results in stress shielding and increases the risk of bone resorption, but its findings were based on subjective radiological assessment. This study aimed to verify this hypothesis and to objectively quantify medial tibial bone density by using serial measurements with digital radiological densitometry. METHODS: This was a retrospective cohort study involving 140 patients (70 thick tray vs. 70 thin tray) with cobalt-chromium implants with at least 24 months of follow-up. Standard radiographs were reviewed to look for incidence of medial tibial bone loss. Serial measurement of medial tibial bone density was also performed using the method of digital radiological densitometry. RESULTS: There was no significant difference in the incidence of medial tibial bone loss. Both groups showed a significant drop in medial tibial bone density after operation (P < 0.01). Medial tibial bone density of the thick-tray cohort was significantly higher than the thin-tray cohort at one year (93.3 vs. 83.1 Greyscale; P = 0.04), but not at two and three years. Clinical outcomes in terms of postoperative range of motion, Knee Society score and complication rates were similar. CONCLUSIONS: Medial tibial bone resorption is a common phenomenon. Implants with thicker tibial trays suffer less than those with thinner trays at one year, but the difference is transient and does not affect clinical outcome.

Treatment of Intracranial Aneurysms with Flow Re-direction Endoluminal Device - A Single Centre Experience with Short-term Follow-up Results.

PURPOSE: A flow diverter (FD) is an effective treatment option for intracranial aneurysms. The Flow Re-direction Endoluminal Device (FRED) is a relatively new flow diverter with a unique dual-layer design. We report our experience and short-term results with the FRED. MATERIALS AND METHODS: We did a retrospective review of all consecutive cases in which the FRED was used to treat intracranial aneurysms at a single institution from March 2014 till December 2015. Clinical parameters, aneurysm characteristics, technical results and short-term outcomes were reviewed. RESULTS: Eleven intracranial aneurysms were treated with the FRED in 11 patients. The technical device deployment success rate was 100%. Immediate reduction in intra-aneurysmal flow after deployment was noted in 10 cases. The aneurysm occlusion rate at 6 months was 75%. There was 1 complication of in-stent thrombosis immediately after deployment. There was no side branch occlusion, delayed aneurysm rupture, stroke, or intraparenchymal haemorrhage. There was no neurological deficit, morbidity, or mortality. CONCLUSION: The FRED is a new FD. It has shown to be safe and effective in our series. The unique dual-layer design of the device renders it to have technical advantages over other FDs. The 6-month aneurysm occlusion rate and complication profile of FRED are similar to other FDs.

Blood Sparing Efficacy of Oral Tranexamic Acid in Primary Total Knee Arthroplasty: A Randomized Controlled Trial.

PURPOSE: Tranexamic acid (TXA) is effective in reducing blood loss in primary total knee replacement. Almost all studies used an intravenous form or a topical form. The aim of this study was to assess the blood sparing efficacy and the safety of oral TXA. MATERIALS AND METHODS: All patients with primary total knee replacement performed in our institute from January 2015 to October 2015 were eligible. Oral TXA group was given 1 g oral TXA 2 hours before induction of anesthesia and 6 hours and 12 hours postoperatively. The control group was not given TXA. RESULTS: There were 94 cases in the oral TXA group and 95 cases in the control group. There was no difference in the baseline characteristics. The oral TXA group had a significantly lower hemoglobin drop (1.7 g/dL vs. 2.5 g/dL), lower drain output (154 mL vs. 203 mL), lower hidden blood loss (244 mL vs. 423 mL) and lower total blood loss (398 mL vs. 626 mL). There was no difference in transfusion rate (1.1% vs. 3.2%) and thromboembolic complication. There was no infection or mortality in both groups. CONCLUSIONS: Oral TXA is effective in reducing blood loss in primary total knee replacement. It is a safe alternative to the intravenous or topical form.

Blood-Sparing Efficacy of Oral Tranexamic Acid in Primary Total Hip Arthroplasty.

BACKGROUND: Tranexamic acid (TXA) has been shown to be effective in reducing blood loss, hemoglobin drop, and blood transfusion in primary total hip arthroplasty. Most studies used intravenous form or topical form. This study was to assess the blood-sparing efficacy and safety of oral TXA in total hip arthroplasty. METHODS: Patients with primary total hip arthroplasty from 2012 to 2015 were recruited. Trial group with 1 gm of oral TXA 2 hours preoperatively, and 6 hours and 12 hours postoperatively was compared with the control group without drug. Outcome measures were intraoperative blood loss, drain output, observed total blood loss, actual total blood loss, hidden blood loss, hemoglobin drop, blood transfusion requirement, thromboembolic complications, cerebrovascular or cardiovascular complications, and mortality. RESULTS: After exclusion, 108 patients were included-54 in trial group and 54 in control group. There was no significant difference in the baseline characteristics. The trial group had significantly higher postoperative hemoglobin (10.3 vs 9.4 g/dL), lower hemoglobin drop (3.0 vs 4.1 g/dL), lower hidden blood loss (149 vs 354 mL), and lower actual total blood loss (847 vs 1096 mL). There was no significant difference in thromboembolic complications or mortality. There was also no periprosthetic infection or drug allergy. CONCLUSION: Oral TXA is effective in blood sparing in terms of reduction in hemoglobin drop, hidden blood loss, and actual total blood loss. It is safe and is an alternative to the intravenous or topical form.

Rare presentation of small bowel intussusception in childhood.

Small bowel intussusception complicated simultaneously by volvulus in an older child is rare but clinically significant, necessitating urgent operative management. We report a local case of jejuno-jejunal intussusception complicated by volvulus and bowel infarction in a 9-year-old Chinese girl, with diagnosis made on preoperative computed tomography and confirmed at laparotomy. An intestinal polyp as the lead point for intussusception was identified operatively.

Short duration and low suction pressure drain versus no drain following total knee replacement.

PURPOSE: To compare the short-term outcome in patients with or without a drain (short duration and low suction pressure) following total knee replacement (TKR). METHODS: A consecutive series of 106 women and 48 men (mean age, 69 years) underwent unilateral TKR. The first 77 patients used a low suction pressure (200 mm Hg) drain following TKR for 24 hours, and the next 77 patients used no drain. RESULTS: The 2 groups were comparable in terms of preoperative characteristics, the proportion of patients with pharmacological prophylaxis for deep vein thrombosis, the tourniquet time, and mode of anaesthesia. The mean drain output in the drain group was 221 ml. The time to achieve straight-leg-raising was earlier in the drain group (3.1 vs. 4.2 days, p<0.001). CONCLUSION: The use of a short duration, low suction pressure drain following TKR enabled an earlier return of quadriceps power, without increasing haemoglobin drop and transfusion rate.

Risk factors for periprosthetic joint infection in total knee arthroplasty.

PURPOSE: To evaluate the incidence and risk factors of periprosthetic joint infection (PJI) in patients undergoing total knee arthroplasty (TKA) in a high-volume hospital. METHODS: Records of 1133 primary TKAs were reviewed. Correlation between surgery volume and infection rate was determined. Risk factors for PJI were identified using case-control analysis of variables. TKAs performed between October 2012 and March 2013 without infection were used as controls. RESULTS: Of 1133 TKAs, 8 (0.71%) PJI occurred. The organisms involved were Staphylococcus aureus (n=4), coagulase-negative staphylococci (n=2), Pseudomonas aeruginosa (n=1), and methicillin-resistant S aureus (n=1). In the 6-month period chosen as the control period, one (0.52%) out of 192 TKAs developed PJI. Hospital annual volume did not correlate with infection rate (p=0.766). Significant risk factors included young age, comorbidities such as diabetes, anaemia, thyroid disease, heart disease, lung disease, and long operating time. Six of the 8 patients with PJIs had at least one risk factor. However, the number of patients with infection was too small to have sufficient power. CONCLUSION: Comorbidities are a risk factor for PJI. Perioperative optimisation of comorbidities and the use of antibiotic-loaded cement in patients with severe comorbidities should be considered.

Blood management protocol for total knee arthroplasty to reduce blood wastage and unnecessary transfusion.

PURPOSE: To compare outcomes of 2 cohorts of patients who underwent total knee arthroplasty (TKA) before and after the introduction of a blood management protocol. METHODS: Records of 97 and 96 consecutive patients who underwent unilateral TKA before and after introduction of the blood management protocol, respectively, were reviewed. Before introduction of the protocol, patients were cross-matched for blood before surgery. Transfusion after surgery was at the discretion of the surgeons or the on-call doctors. After introduction of the protocol, only patients with a preoperative haemoglobin level of <110 g/l underwent 'type and screening' of blood group. 2 units of blood were cross-matched preoperatively when multiple red-cell antibodies were identified or postoperatively when blood transfusion was required. Only patients with a postoperative haemoglobin level of <80 g/l or being symptomatic received blood transfusion until the haemoglobin level reached >100 g/l. Those with a postoperative haemoglobin level of 80 to 100 g/l were given iron sulphate 300 mg twice daily for a month. RESULTS: The 2 groups did not differ significantly in age, sex ratio, pre- and post-operative haemoglobin levels, and drain output. Comparing outcome before and after introduction of the protocol, the transfusion rate (10.3% vs. 3.1%, p=0.046), crossmatch rate (100% vs. 3.1%, p<0.001), and crossmatch to transfusion ratio (9.7:1 vs. 1:1, p<0.001) decreased. Among transfused patients, the decreased postoperative haemoglobin level indicated a lower transfusion trigger point (100 g/l vs. 75 g/l, p<0.006) No patient developed infection, cardiovascular or cerebrovascular complications within 30 days. CONCLUSION: The blood management protocol for TKA is effective in reducing unnecessary allogeneic blood transfusions and wastage of unused blood, without an increase in postoperative complications.

Effect of patellar thickness on early results of total knee replacement with patellar resurfacing.

PURPOSE: Patellar thickness is a concern in total knee replacement with patellar resurfacing because of the risk of patellar fracture or implant loosening. The aim of this study was to evaluate if patellar thickness is related to clinical outcome in the absence of patellar fracture or implant loosening. METHODS: Early results of 169 patients who underwent total knee replacement with patellar resurfacing were reviewed to assess the effect of patellar thickness on clinical outcome. The mean follow-up was 13 months. The range of motion, Knee Society Score, Function Score and WOMAC Score were assessed preoperatively, at day 0, 6 months and 1 year. Radiographs were assessed for patellar fracture or implant loosening. RESULTS: Thirty-one percent of all patients had preoperative thickness <21 mm. Seven percent had <12 mm residual thickness after patellar cut, all were female. Twenty-three percent had ≥1 mm increase of thickness after surgery. Radiographs did not show any patellar fracture or implant loosening. However, preoperative patellar thickness <21 mm had poorer gain in range of motion at 1 year. Preoperative range of motion had greater influence on postoperative range of motion than preoperative patellar thickness. Residual thickness <12 mm had lower gain in WOMAC score at 1 year and an increase in thickness ≥1 mm postoperatively was associated with lower gain in WOMAC score at 6 months. CONCLUSIONS: Early results of patellar resurfacing with preoperative thickness <21 mm or residual thickness <12 mm were found to be inferior even in the absence of patellar fracture or implant loosening. Conservative cutting resulting in 1 mm increase in thickness was also found to have inferior clinical results. LEVEL OF EVIDENCE: II.

Single-laboratory validation of a method for the determination of vitamin D3 in dietary supplements by liquid chromatography with tandem mass spectrometry (LC-MS/MS).

A single-laboratory validation (SLV) for the analysis of vitamin D3 was performed in four types of dietary supplements (capsules, soft gels, syrups, and tablets) using LC-MS/MS. Samples were treated by alkaline saponification for oil-based soft gels and utilized EDTA solution for capsules, syrups, and tablets prior to n-hexane extraction. Vitamin D3 in sample extracts was separated on a reversed-phase C18 column (100 x 2.1 mm, 2.7 pm) using a mobile phase of a 95 + 5 (v/v) mixture of 5 mM ammonium formate in methanol containing 0.1% formic acid and 5 mM ammonium formate in 0.1% formic acid running at a flow rate of 0.2 mL/min. Vitamin D3 was confirmed by the presence of three fragment ions at m/z 107, 159, and 259 within a defined retention time window from the precursor ion at m/z 385. Quantitation was based on the peak area at m/z 367 to that of the internal standard (d3-vitamin D3) at m/z 370 with reference to the respective response ratios of the calibration standards. The linear response of vitamin D3 ranged from 0.10 to 6.29 mg/L and the correlation coefficient (r) of the six-point calibration curves was > 0.999. Accuracy, in terms of the spiked recoveries from blank syrup and starch powder at three different concentration levels, was 101-103%. Precision, determined by two different analysts over a period of 5 weeks, ranged from 2.7 to 7.0% for the four preparations. The SLV demonstrates the present LC-MS/MS method is reliable and robust for the determination of vitamin D3 in the studied dietary supplements. Considering the attainment of satisfactory SLV results, further validation through intra-laboratory collaborative study is recommended.

Single-Laboratory Validation of a Method for the Determination of Vitamin D3 in Dietary Supplements by Liquid Chromatography with Tandem Mass Spectrometry (LC-MS/MS).

A single-laboratory validation (SLV) for the analysis of vitamin D3 was performed in four types of dietary supplements (capsules, soft gels, syrups, and tablets) using LC-MS/MS. Samples were treated by alkaline saponification for oil-based soft gels and utilized EDTA solution for capsules, syrups, and tablets prior to n-hexane extraction. Vitamin D3 in sample extracts was separated on a reversed-phase C18 column (100 × 2.1 mm, 2.7 µm) using a mobile phase of a 95 + 5 (v/v) mixture of 5 mM ammonium formate in methanol containing 0.1% formic acid and 5 mM ammonium formate in 0.1% formic acid running at a flow rate of 0.2 mL/min. Vitamin D3 was confirmed by the presence of three fragment ions at m/z 107, 159, and 259 within a defined retention time window from the precursor ion at m/z 385. Quantitation was based on the peak area at m/z 367 to that of the internal standard (d3-vitamin D3) at m/z 370 with reference to the respective response ratios of the calibration standards. The linear response of vitamin D3 ranged from 0.10 to 6.29 mg/L and the correlation coefficient (r) of the six-point calibration curves was >0.999. Accuracy, in terms of the spiked recoveries from blank syrup and starch powder at three different concentration levels, was 101-103%. Precision, determined by two different analysts over a period of 5 weeks, ranged from 2.7 to 7.0% for the four preparations. The SLV demonstrates the present LC-MS/MS method is reliable and robust for the determination of vitamin D3 in the studied dietary supplements. Considering the attainment of satisfactory SLV results, further validation through intra-laboratory collaborative study is recommended.

Performance evaluation of polycyclic aromatic hydrocarbons analysis in sediment from proficiency testing with metrological reference values.

This paper describes a metrological approach to evaluate the measurement capability of laboratories participating in two proficiency testing (PT) programmes involving the analysis of five polycyclic aromatic hydrocarbons (PAHs) in sediment samples. Reference values of PAHs in the programmes for performance assessment were obtained from an accurate isotope dilution gas chromatography mass spectrometry (ID-GCMS) method which was thoroughly validated and verified. Isotope dilution mass spectrometry (IDMS) technique usually has a well-defined measurement uncertainty budget and a traceability link to an International System of Units. Provision of the metrological reference values in PT enables the establishment of a technical platform to assess the actual competence of the participating laboratories in sediment PAHs analysis. Results of the PT programmes showed that about 80 % of the laboratories employed gas chromatography in their analyses and the remaining used liquid chromatography. Irrespective of the techniques being used, however, the majority of the participating laboratories were observed to underestimate values in which the mean values of the five reported PAHs were less than those of the ID-GCMS-derived reference values by 13-20 %. Only 41-44 % of the participating laboratories were able to achieve satisfactory z-scores. The present study revealed that the reinforcement of the capability for accurate measurement of PAHs in sediment samples in laboratories worldwide should be addressed.