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* Context.--Total serum bilirubin (TSB) analysis is pivotal for diagnosing neonatal hyperbilirubinemia. Because of a routine change in laboratory equipment, our TSB assay changed from a diazo to a vanadate oxidase method. Upon implementation, TSB results were substantially higher in newborns than expected based on the validation. Objective.--To investigate the application of TSB and intermethod differences in neonates and their impact on phototherapy treatment. Design.--The diazo and vanadate methods were compared directly using neonatal and adult samples. Anonymized external quality control data were analyzed to explore interlaboratory differences among 8 commercial TSB assays. Clinical patient data were extracted from the medical records to investigate the number of newborns receiving phototherapy. Results.--The mean bias of the vanadate versus the diazo TSB method was +17.4% and +3.7% in neonatal and adult samples, respectively. External quality control data showed that the bias of commercial TSB methods compared with the reference method varied from -3.6% to +20.2%. Within-method variation ranged from 5.2% to 16.0%. After implementation of the vanadate TSB method, the number of neonates treated with phototherapy increased approximately threefold. Conclusions.--Currently available TSB assays lack harmonization for the diagnosis of neonatal hyperbilirubinemia. Between-methods differences are substantially higher in neonatal compared with adult samples, highlighting the importance of including neonatal samples during assay validation. Close collaboration between laboratory specialists and clinicians is essential to prevent overtreatment or undertreatment upon the implementation of novel analyzers or assays. Also, harmonization of TSB assays, with an emphasis on neonatal application, is warranted. (Arch Pathol Lab Med. 2024;148:e40-e47; doi: 10.5858/arpa.2022-0478-OA), Neonatal jaundice is a usually benign condition with an estimated incidence of more than 60% in full-term newborns. (1) It is caused by an increase of unconjugated bilirubin, which is [...]

In 14 overweight women, 24-h energy expenditure (EE) was measured in a whole-body indirect calorimeter: before weight reduction (100% diet), after 1 wk on a 4.2-MJ diet, after 8 wk on 4.2-MJ diet, after weight reduction on 100% diet. Data of two subjects were excluded. Mean body weight declined from 93.3 ± 7.4 (mean ± SD) to 83.4 ± 7.7 kg; 24-hEE decreased from 10.52 ± 0.83 MJ on the 100% diet to 9.58 ± 0.75 Mi on the 4.2-Mi diet. After 8 wk, 24-hEE had decreased by 15% of the initial 24-hEE to 8.92 ± 0.65 Mi. After refeeding (1 wk), it increased to 9.45 ± 0.75 MJ. Calculated energy requirement before weight reduction was 10.62 ± 0.88 MJ/day; after weight reduction, 9.39 ± 0.79 MJ/day. The decrease was more than that predicted from the change in body weight and body composition. An adaptation probably occurs, which may be metabolic. [ABSTRACT FROM AUTHOR]