Summary. Anecdotal experience with full blood count (FBC) technology incorporating analysis of depolarized laser light (DLL) for the enumeration of eosinophils showed that malaria infection generated unusual distributions in the white cell channels. The objective of this study was to identify and define criteria for a diagnosis of malaria using this technology. To determine sensitivity, specificity, and positive and negative predictive values, 224 directed samples referred specifically for malaria were used; true positives were defined as those in which malaria was identified by microscopic and/or immunological methods. For the DLL method, positive was defined as one or more large mononuclear cell(s) for which the 90Њ depolarized signal exceeded the 90Њ polarized signal. To determine possible utility in a routine haematology laboratory setting, 220 random undirected FBC samples were evaluated for possible malaria infection by the DLL method. Of the 224 directed samples, 95 were malaria positive as determined by microscopic and/or immunological methods, and 129 were negative. For the DLL method, overall sensitivity was 72% (90% in the case of Black Africans), and specificity 96%. Positive and negative predictive values overall were 93% and 82% respectively. In the utility study a single positive result was identified among the 220 samples studied. This was found to be from a patient with malaria. The detection of unexpected malaria by automated screening FBC analysis could substantially lower the mortality and morbidity from unascertained infection, especially in indigenous African peoples.

Immunoglobulin (Ig) and T-cell receptor (TCR) gene rearrangements provide clonal markers useful for diagnosis and measurement of minimal residual disease (MRD) in acute lymphoblastic leukemia (ALL). We analyzed the sequences of Ig and TCR gene rearrangements obtained at presentation and relapse in 41 children with ALL to study clonal stability, which has important implications for monitoring MRD, during the course of the disease. In 42%, all original Ig and/or TCR sequences were conserved. In 24%, one original sequence was preserved but the other lost, and in 14% the original sequences were conserved with new sequences identified at relapse. In 20% only new sequences were found at relapse. Using primers designed from the novel relapse sequences, the relapse clone could be identified as subdominant clones in the diagnostic sample in 8 of 14 patients. Alteration of these clonal gene rearrangements is a common feature in childhood ALL. MRD IntroductionAdvances in cytogenetic and immunophenotypic characterization have greatly improved the diagnostic accuracy and risk assignment of childhood acute lymphoblastic leukemia (ALL) 1 resulting in cure rates approaching 80%, 2,3 however relapse still occurs in about 20% of children. Monitoring of minimal residual disease (MRD) has proved useful for predicting which children will relapse. [4][5][6][7][8][9][10] Most studies of MRD detection in pediatric ALL have used polymerase chain reaction (PCR)-based techniques. 4,8,10,11 Immunoglobulin heavy chain (IgH) and T-cell receptor (TCR) gene rearrangements appear to be excellent patient-specific PCR targets for MRD detection, but, of concern, these rearrangements may be unstable due to clonal evolution during the course of the disease. [12][13][14][15][16][17] Rearranged Ig and TCR genes have been used as molecular markers for characterization of clonality of lymphoid cell population. 11,18,19 Generally, it is assumed that the relapses result from outgrowth of residual leukemic cells that persist in patients below the limits of detection of standard techniques. 19,20 It has also been postulated that the "original" leukemia may in some cases be cured, but a "new," therapy-related secondary leukemia can develop. 21 Discrimination between those cases that relapse because of the re-emergence of the initial ALL and the occurrence of secondary ALL might be clinically important to guide subsequent therapy. A number of studies using Southern blotting or PCR amplification have previously demonstrated diverse patterns of the antigen receptor gene rearrangements in a larger proportion (10%-40%) of relapsed childhood ALL. [22][23][24] Sequence analysis has provided some insight into the molecular mechanisms that account for altered rearrangement patterns, including ongoing rearrangements (eg, V H to D H J H joining, V H -V H replacement, and "open-and-shut" mechanism), disappearance of initial clone/subclones, and generation of new clone/subclones. [13][14][15][24][25][26] TCR and Ig kappa delete element (Ig-de) rearrangements have been...

Critical illness in COVID-19 is an extreme and clinically homogeneous disease phenotype that we have previously shown1 to be highly efficient for discovery of genetic associations2. Despite the advanced stage of illness at presentation, we have shown that host genetics in patients who are critically ill with COVID-19 can identify immunomodulatory therapies with strong beneficial effects in this group3. Here we analyse 24,202 cases of COVID-19 with critical illness comprising a combination of microarray genotype and whole-genome sequencing data from cases of critical illness in the international GenOMICC (11,440 cases) study, combined with other studies recruiting hospitalized patients with a strong focus on severe and critical disease: ISARIC4C (676 cases) and the SCOURGE consortium (5,934 cases). To put these results in the context of existing work, we conduct a meta-analysis of the new GenOMICC genome-wide association study (GWAS) results with previously published data. We find 49 genome-wide significant associations, of which 16 have not been reported previously. To investigate the therapeutic implications of these findings, we infer the structural consequences of protein-coding variants, and combine our GWAS results with gene expression data using a monocyte transcriptome-wide association study (TWAS) model, as well as gene and protein expression using Mendelian randomization. We identify potentially druggable targets in multiple systems, including inflammatory signalling (JAK1), monocyte–macrophage activation and endothelial permeability (PDE4A), immunometabolism (SLC2A5 and AK5), and host factors required for viral entry and replication (TMPRSS2 and RAB2A).

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