Amy Henderson

OBJECTIVES: To evaluate the continued impact of pulse oximetry screening (POS) in a regional neonatal unit (NNU) and identify trends in screening outcomes in comparison with our previous experience. DESIGN: Retrospective review of admissions between April 2013 and March 2019 (the current study) and comparison with previously published data (the 2014 study). PATIENTS: All infants >34 weeks completed gestation admitted to NNU as a result of positive POS. OUTCOME MEASURES: Indication for admission, diagnosis, investigations and management. RESULTS: There were 49 375 livebirths and 253 NNU admissions as a result of positive POS (0.5% of livebirths; compared with 0.8% in 2014). 247/253 (97.6%) of those admitted had a significant diagnosis requiring medical intervention (compared with 79% in 2014) and the proportion of healthy babies (with transitional circulation) admitted decreased from 21% to 2.4%.22 (9%) babies admitted as a result of a positive POS were found to have a previously undiagnosed congenital heart defect (CHD) of which eight were critical CHDs (CCHDs). This accounted for 73% of all undiagnosed CCHD undergoing POS. The antenatal detection rate of CCHD was 75% compared with 46% in 2014. No baby died or collapsed on the postnatal ward during the study period. The proportion of babies with CCHD identified before discharge improved from 94% to 99%. CONCLUSIONS: Routine POS, in addition to antenatal screening and postnatal examination, continues to contribute to the improvement of our overall CCHD detection rates. We have demonstrated an overall reduction in the admission of healthy babies and therefore workload following a positive test.

We adapted previously published methods for nonspecific esterase and alkaline phosphatase staining of white blood cells in suspension for use on a Technicon H-1 hematology analyzer. The objective was to develop a semiautomated method using whole blood that could be employed on a large scale for hematology laboratory applications, including toxicology studies, measurement of neutrophil left shift, and cytochemical classification of myeloid leukemias. The nonspecific esterase method uses the pararosaniline stain, generating the unstable substrate from two stable precursors. Whole blood is added to the substrate plus dye mix. Next, acid lysis and fixation steps destroy red cells and stabilize the monocyte staining. The alkaline phosphatase stain employs a stable naphthyl phosphate substrate and fast blue B coupling dye. The red cells are lysed with a pH 10.3 propanediol buffer, and the white blood cells are then stabilized with formalin fixation. For both methods the staining is performed off-line, and the sample is then diluted with propanediol to match the refractive index of the sheath on the H-1 analyzer, before aspiration into the direct cytometry port. A cytogram of scattered versus absorbed light is obtained. The number of cells staining and the intensity of the stain can be quantified from the cytogram.