Harmonization of indirect reference intervals calculation by the Bhattacharya method.

OBJECTIVES: The aim of this study was to harmonize the criteria for the Bhattacharya indirect method Microsoft Excel Spreadsheet for reference intervals calculation to reduce between-user variability and use these criteria to calculate and evaluate reference intervals for eight analytes in two different years. METHODS: Anonymized laboratory test results from outpatients were extracted from January 1st 2018 to December 31st 2019. To assure data quality, we examined the monthly results from an external quality control program. Reference intervals were determined by the Bhattacharya method with the St Vincent's hospital Spreadsheet firstly using original criteria and then using additional harmonized criteria defined in this study. Consensus reference intervals using the additional harmonized criteria were calculated as the mean of four users' lower and upper reference interval results. To further test the operation criteria and robustness of the obtained reference intervals, an external user validated the Spreadsheet procedure. RESULTS: The extracted test results for all selected laboratory tests fulfilled the quality criteria and were included in the present study. Differences between users in calculated reference intervals were frequent when using the Spreadsheet. Therefore, additional criteria for the Spreadsheet were proposed and applied by independent users, such as: to set central bin as the mean of all the data, bin size as small as possible, at least three consecutive bins and a high proportion of bins within the curve. CONCLUSIONS: The proposed criteria contributed to the harmonization of reference interval calculation between users of the Bhattacharya indirect method Spreadsheet.

Comparison of four indirect (data mining) approaches to derive within-subject biological variation.

OBJECTIVES: Within-subject biological variation (CVi ) is a fundamental aspect of laboratory medicine, from interpretation of serial results, partitioning of reference intervals and setting analytical performance specifications. Four indirect (data mining) approaches in determination of CVi were directly compared. METHODS: Paired serial laboratory results for 5,000 patients was simulated using four parameters, d the percentage difference in the means between the pathological and non-pathological populations, CVi the within-subject coefficient of variation for non-pathological values, f the fraction of pathological values, and e the relative increase in CVi of the pathological distribution. These parameters resulted in a total of 128 permutations. Performance of the Expected Mean Squares method (EMS), the median method, a result ratio method with Tukey's outlier exclusion method and a modified result ratio method with Tukey's outlier exclusion were compared. RESULTS: Within the 128 permutations examined in this study, the EMS method performed the best with 101/128 permutations falling within ±0.20 fractional error of the 'true' simulated CVi , followed by the result ratio method with Tukey's exclusion method for 78/128 permutations. The median method grossly under-estimated the CVi . The modified result ratio with Tukey's rule performed best overall with 114/128 permutations within allowable error. CONCLUSIONS: This simulation study demonstrates that with careful selection of the statistical approach the influence of outliers from pathological populations can be minimised, and it is possible to recover CVi values close to the 'true' underlying non-pathological population. This finding provides further evidence for use of routine laboratory databases in derivation of biological variation components.

Assessment and application of Marfey's reagent and analogs in enantioseparation: a decade's perspective.

Of the various methods available for high-performance liquid chromatography separation of enantiomers (of e.g. amino acids and amino group containing compounds) by the pre-column derivatization approach, use of Marfey's reagent has been most successful with continued application since its introduction in 1984. The reagent is prepared from difluoro dinitro benzene by nucleophilic substitution of one of its F atoms by l-alanine amide. There is flexibility to prepare several chiral variants (by substituting the F atom with different chiral auxiliaries) and to tailor the hydrophobicity and resolution, ultimately, of the diastereomeric derivatives. The present paper assesses and reviews applications of Marfey's reagent and its chiral variants (i.e. other FDNP reagents) for enantioseparation of certain amino group containing drugs/amino acids, and to provide some case studies on enantiomeric separations that are important for the pharmaceutical industry. Various explanations for separation mechanism and elution order using FDNP reagents are included and the question of the configuration of the corresponding enantiomer using an indirect approach has also been addressed.

Feasibility of using real-world free thyroxine data from the US and Europe to enable fast and efficient transfer of reference intervals from one population to another.

Objectives: The direct approach for determining reference intervals (RIs) is not always practical. This study aimed to generate evidence that a real-world data (RWD) approach could be applied to transfer free thyroxine RIs determined in one population to a second population, presenting an alternative to performing multiple RI determinations. Design and methods: Two datasets (US, n = 10,000; Europe, n = 10,000) were created from existing RWD. Descriptive statistics, density plots and cumulative distributions were produced for each data set and comparisons made. Cumulative probabilities at the lower and upper limits of the RIs were identified using an empirical cumulative distribution function. According to these probabilities, estimated percentiles for each dataset and estimated differences between the two sets of percentiles were obtained by case resampling bootstrapping. The estimated differences were then evaluated against a pre-determined acceptance criterion of ≤7.8% (inter-individual biological variability). The direct approach was used to validate the RWD approach. Results: The RWD approach provided similar descriptive statistics for both populations (mean: US = 16.1 pmol/L, Europe = 16.4 pmol/L; median: US = 15.4 pmol/L, Europe = 15.8 pmol/L). Differences between the estimated percentiles at the upper and lower limits of the RIs fulfilled the pre-determined acceptance criterion and the density plots and cumulative distributions demonstrated population homogeneity. Similar RI distributions were observed using the direct approach. Conclusions: This study provides evidence that a RWD approach can be used to transfer RIs determined in one population to another.

Calculation of reference intervals for the concentrations of α-tocopherol and retinol in serum using indirect data-mining procedures.

BACKGROUND: Establishing adequate reference intervals (RIs) for vitamins A and E is essential for diagnosing and preventing deficiencies. Due to the current boom in data mining and its easy applicability, more laboratories are establishing RIs using indirect methods. Our study aims to obtain RIs using four indirect data-mining procedures (Bhattacharya, Hoffmann, Kosmic, and RefineR) for vitamins A and E. MATERIAL AND METHODS: 8943 individuals were collected to establish the RIs. After using different data cleaning steps and checking whether these data should be divided according to age and gender based on multiple linear regression and variance component analyses, indirect RIs were calculated using specific Excel spreadsheets or R-packages software. RESULTS: A total of 2004 records were eligible. For vitamin A, the RIs obtained were (1.11 - 2.68) µmol/L, (1.13 - 2.70) µmol/L, (1.13 - 2.71) µmol/L, and (1.17 - 2.66) µmol/L using the Bhattacharya, Hoffmann, Kosmic and RefineR approaches, respectively. For vitamin E, these intervals were (17.3 - 49.9) µmol/L (Bhattacharya), (17.3 - 48.9) µmol/L (Hoffmann), (19.6 - 50.3) µmol/L (Kosmic), and (19.4 - 50.9) µmol/L (RefineR). In all cases, the RIs were comparable. CONCLUSIONS: Suitable RIs for vitamins A and E were calculated using four indirect methods that are suitable and adapted to our population's demographic characteristics.

Chinese pediatric and adolescent reference intervals of vitamin E based on real-world physical examination data.

OBJECTIVES: To establish the reference interval (RI) of vitamin E for Chinese children and adolescents. MATERIALS AND METHODS: Serum tocopherol samples were examined using high performance liquid chromatography in third-party clinical laboratory institutions. Using real-world data from multi-center clinical laboratory institutions in China, the distribution parameters of vitamin E levels were described and the RI was calculated using three algorithms. RESULTS: A total of 756,766 cases were included in the analysis, including 435,561 males and 321,205 females. The median of vitamin E in infants younger than 4 years of age initially increased but subsequently decreased; while its levels in children between 4 and 11 years of age remained relatively stable despite progressing in age (approximately 7.4-7.8 mg/L). After the start of puberty, the difference, relative to sex, gradually became apparent, and the median vitamin E levels in females was higher than in males. The differences of vitamin E levels between different regions and samples in different seasons had no clinical significance. The RI of vitamin E for children aged 0-18 years in China was 4.5-11.1 mg/L based on expectation-maximization algorithm. The RI established by the Hoffmann method was 4.6-12.8 mg/L. CONCLUSION: The age- and sex-specific RIs of vitamin E were established by an indirect approach. The RIs established by EM algorithms could be used as an alternative to establish RIs based on real-world data.

Comparison of two (data mining) indirect approaches for between-subject biological variation determination.

BACKGROUND: Between-subject biological variation (CVg) is an important parameter in several aspects of laboratory practice, including setting of analytical performance specification, delta checks and calculation of index of individuality. Using simulations, we compare the performance of two indirect (data mining) approaches for deriving CVg. METHODS: The expected mean squares (EMS) method was compared against that proposed by Harris and Fraser. Using numerical simulations, d the percentage difference in the mean between the non-pathological and pathological populations, CVi the within-subject coefficient of variation of the non-pathological distribution, f the fraction of pathological values, and e the relative increase in CVi of the pathological distribution were varied for a total of 320 conditions to examine the impact on the relative fractional of error of the recovered CVg compared to the true value. RESULTS: Comparing the two methods, the EMS and Harris and Fraser's approaches yielded similar performance of 158 conditions and 157 conditions within ± 0.20 fractional error of the true underlying CVg, for the normal and lognormal distributions, respectively. It is observed that both EMS and Harris and Fraser's method performed better using the calculated CVi rather than the actual ('presumptive') CVi. The number of conditions within 0.20 fractional error of the true underlying CVg did not differ significantly between the normal and lognormal distributions. The estimation of CVg improved with decreasing values of f, d and CViCVg. DISCUSSIONS: The two statistical approaches included in this study showed reliable performance under the simulation conditions examined.

Dynamic trend in alkaline phosphatase activity in infants aged 0-12 months revealed by an indirect approach.

OBJECTIVE: Alkaline phosphatase (ALP) is a ubiquitous enzyme in humans that can be used for diagnosing childhood diseases. Infants have the highest rapid growth rate and are susceptible to metabolic bone diseases. In infants, ALP activities exhibit significant month-wise variations, and authoritative standards are lacking. The present study aimed to provide a reference for the diagnosis of diseases related to abnormal ALP activities in infants. METHODS: This study included 24,618 samples collected from infants aged 0-12 months from three medical centers in Chongqing, China. Samples of infants diagnosed with diseases that may affect ALP activity have been exclude. ALP activity was analyzed using an automatic biochemical analyzer. A percentile curve for ALP activity in male and female infants was constructed using MATLAB, and the skewness-median-coefficient of variation method was employed for curve fitting. RESULTS: ALP activity in male and female infants peaked at 0-4 months; the peak appeared at 1-2 months and declined gradually thereafter. After 4-5 months of age, the ALP activities declined further, with the lowest values observed at 11-12 months of age. A comparison between the data from this study and a those from a published German study indicates that Chinese infants exhibited peak ALP activity later and subsequent decline greater than German infants. CONCLUSIONS: A percentile curve was constructed for month-wise ALP activity in male and female infants, which could provide a reference for diagnosing diseases related to abnormal ALP activity in infants.

Comparison of 8 methods for univariate statistical exclusion of pathological subpopulations for indirect reference intervals and biological variation studies.

BACKGROUND: Indirect reference intervals and biological variation studies heavily rely on statistical methods to separate pathological and non-pathological subpopulations within the same dataset. In recognition of this, we compare the performance of eight univariate statistical methods for identification and exclusion of values originating from pathological subpopulations. METHODS: The eight approaches examined were: Tukey's rule with and without Box-Cox transformation; median absolute deviation; double median absolute deviation; Gaussian mixture models; van der Loo (Vdl) methods 1 and 2; and the Kosmic approach. Using four scenarios including lognormal distributions and varying the conditions through the number of pathological populations, central location, spread and proportion for a total of 256 simulated mixed populations. A performance criterion of ± 0.05 fractional error from the true underlying lower and upper reference interval was chosen. RESULTS: Overall, the Kosmic method was a standout with the highest number of scenarios lying within the acceptable error, followed by Vdl method 1 and Tukey's rule. Kosmic and Vdl method 1 appears to discriminate better the non-pathological reference population in the case of log-normal distributed data. When the proportion and spread of pathological subpopulations is high, the performance of statistical exclusion deteriorated considerably. DISCUSSIONS: It is important that laboratories use a priori defined clinical criteria to minimise the proportion of pathological subpopulation in a dataset prior to analysis. The curated dataset should then be carefully examined so that the appropriate statistical method can be applied.

Indirect Arthroscopic Distal Clavicle Resection: an Institutional Experience with Midterm Functional Outcome.

BACKGROUND: Acromioclavicular joint arthritis is a relatively common source of shoulder pain. The treatment options consist of conservative management and operative intervention depending on the severity and duration of the disease. Distal clavicle excision is the standard operative treatment and can be performed through either open or arthroscopic techniques. The purpose of this study was to evaluate the functional outcome of arthroscopic resection of the distal clavicle. MATERIAL AND METHODS: This was a prospective study, conducted in a group of 50 patients in the Post-Gra-duate Department of Orthopaedics, Govt. Medical College Srinagar, from July 2015 to July 2019 with cases followed for a minimum of 3 years. RESULTS: The mean UCLA score improved from 13.2 preoperatively to 29.56 at final follow-up. An excellent result was seen in 10 patients (20%), good in 34 (68%), fair in 3 (6%) and poor in 3 (6%) patients. Overall 88% of the patients achieved excellent or good results and 94% were satisfied. Persistent pain and excessive intraoperative bleeding were the most common complications in our study. CONCLUSIONS: 1. Distal clavicle excision through an indirect or subacromial approach is a safe and effective procedure with very few complications. 2. The subacromial approach gives the added advantage of evaluating any glenohumeral joint and subacromial pathology. 3. This procedure is associated with less pain and improved cosmesis in comparison to open procedures.

Indirect derivation of biological variation data and analytical performance specifications for therapeutic drug monitoring activities.

We applied the indirect approach using anonymised data from an Australian and a Singapore laboratory to derive biological variation data for a group of 10 therapeutic drugs routinely monitored. A series of inclusion and exclusion criteria were applied on the data. The within- (CVi) and between-individual (CVg) biological variation data were then derived as previously described. The corresponding index of individuality and analytical performance specifications were also calculated. The biological variation data were overall very similar between the two study sites. Moreover, the biological variation data were also comparable between males and females, as well as whether the data originated from patients who only had two episodes of measurement during the study period or from the last two results from patients who had more than two episodes of measurement during the study period. The results presented in this study contribute towards the biological variation data for therapeutic drugs, which can be used to inform discussions about the setting of harmonised analytical performance specifications for these measurands.

Working with the parents and families of children with developmental language disorders: An international perspective.

BACKGROUND: The relationship between parental input and child language development has had a complex history. It has become clear that indirect parent training for the parents of children with delayed language development is an important feature of interventions offered by speech and language therapists in the anglophone countries. Yet we know less about how this type of approach is realised in other countries. METHODS: In this paper we report the results of a survey of practice undertaken as part of the work of COST Action IS1406, a European Union (EU) funded research network. The focus of this paper is specifically on parent-related questions and responses referring to children under the age of twelve. The survey was devised by members of the Action and circulated electronically during the summer of 2017. In all, 4024 practitioners responded from 60 countries, the majority of whom came from EU member countries. FINDINGS: Respondents to the survey indicated that indirect therapy is commonly carried out via the parent in the early years and via teachers later. A range of professional groups, in addition to speech and language therapists, is likely to adopt this approach; including teachers, pedagogues and psychologists. A variety of interventions is reported, some of which have a reasonable evidence-base underpinning them. It is interesting to see the widespread involvement of fathers and other family members in interventions. Finally, the fact that practitioner characteristics (age, experience, location of practice etc.) are not related to the use of indirect techniques points to the universal recognition of the value of these approaches. CONCLUSIONS: Despite the very different traditions in the practice of intervention across countries, there is clearly a widespread recognition of the importance of indirect approaches to intervention and specifically those focusing on parents. The mixture of family members being involved in interventions is a very promising indication of the role sharing commonly associated with the contemporary family. Yet the number of specific intervention approaches identified is relatively small given the number of respondents. There is a need for a better understanding of what exactly practitioners are doing when they involve parents in intervention or carry out parent-child interaction interventions and how well these interventions work in routine practice. This also has implications for the application of evidence-based practice and the precise nature of the interventions concerned (advice to parents, video interaction training etc.).