Evaluation of Five Commercial SARS-CoV-2 Antigen Tests in a Clinical Setting

BACKGROUND

Point-of-care antigen tests (AgTs) for the detection of severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) enable the rapid testing of infected individuals and are easy-to-use. However, there are few studies evaluating their clinical use.

OBJECTIVE

The present study aimed to evaluate and compare the clinical performance characteristics of various commercial SARS-CoV-2 AgTs.

DESIGN

The sensitivity of five AgTs, comprising four rapid antigen tests (RAT; AMP Rapid Test SARS-CoV-2 Ag, NADAL COVID-19 Antigen Rapid Test, CLINITEST Rapid COVID-19 Antigen Test, and Roche SARS-CoV-2 Rapid Antigen Test) and one sandwich chemiluminescence immunoassay (CLIA; LIAISON SARS-CoV-2 Assay), were evaluated in 300 nasopharyngeal (NP) swabs. Reverse transcriptase (RT) polymerase chain reaction (PCR) was used as a reference method.

PARTICIPANTS

NP swabs were collected from patients admitted to hospital due to COVID-19.

KEY RESULTS

Sensitivities of the AgTs ranged from 64.9 to 91.7% for samples with RT-PCR cycle threshold (Ct) values lower than 30 and were 100% for cycle threshold (Ct) values lower than 20. The highest sensitivity was observed for CLINITEST Rapid COVID-19 Antigen Test, and Roche SARS-CoV-2 rapid antigen test. Multivariate analysis using time from symptom onset and the Ct value for AgT sensitivity showed an inverse correlation. Further, the female sex was an independent factor of lower RAT sensitivity.

CONCLUSIONS

Antigen tests from NP swab samples show high sensitivity in patients with a Ct value < 20. The best clinical sensitivity can be obtained using AgTs within the first 6 days after symptom onset.

A Rapid, Highly Sensitive and Open-Access SARS-CoV-2 Detection Assay for Laboratory and Home Testing

RT-qPCR-based diagnostic tests play important roles in combating virus-caused pandemics such as Covid-19. However, their dependence on sophisticated equipment and the associated costs often limits their widespread use. Loop-mediated isothermal amplification after reverse transcription (RT-LAMP) is an alternative nucleic acid detection method that overcomes these limitations. Here, we present a rapid, robust, and sensitive RT-LAMP-based SARS-CoV-2 detection assay. Our 40-min procedure bypasses the RNA isolation step, is insensitive to carryover contamination, and uses a colorimetric readout that enables robust SARS-CoV-2 detection from various sample types. Based on this assay, we have increased sensitivity and scalability by adding a nucleic acid enrichment step (Bead-LAMP), developed a version for home testing (HomeDip-LAMP), and identified open-source RT-LAMP enzymes that can be produced in any molecular biology laboratory. On a dedicated website, rtlamp.org (DOI: 10.5281/zenodo.6033689), we provide detailed protocols and videos. Our optimized, general-purpose RT-LAMP assay is an important step toward population-scale SARS-CoV-2 testing.

High frequency of concomitant mastocytosis in patients with acute myeloid leukemia exhibiting the transforming KIT mutation D816V

The KIT mutation D816V is associated with autonomous growth of mast cells (MC) and is detectable in most patients with systemic mastocytosis (SM), including cases with associated hematologic non-MC-lineage disease (AHNMD). Recently, KIT D816V was reported to be expressed in patients with acute myeloid leukemia (AML). However, it was not clarified whether these patients have co-existing occult SM. We investigated neoplastic cells in 101 patients with AML for expression of KIT D816V. In 7/101 patients (6.9%), KIT D816V was detectable. After a thorough histologic, molecular, and biochemical analysis, all 7 cases were found to have an associated SM, leading to the final diagnosis SM-AML. Microdissected tryptase+ MC displayed KIT D816V in all patients tested, whereas CD34+ blasts exhibited KIT D816V in only 2/4 patients. In one AML patient, SM without KIT D816V was detected. In all other patients, no associated SM was found, and leukemic blasts were negative for KIT D816V. In summary, our data show that KIT D816V in AML is highly associated with co-existing SM (SM-AML). Moreover, our data show that AML blasts may lack this transforming target-mutant, which may be important when considering the use of KIT D816V-targeting drugs for treatment of patients with KIT D816V-positive AML.

Splenic Mastocytosis: Report of Two Cases and Detection of the Transforming SomaticC-KITMutation D816V

In the vast majority of patients with systemic mastocytosis (SM), the bone marrow is the primary extracutaneous site of disease. In addition to bone marrow involvement, other visceral organs such as the spleen, liver or the gastrointestinal tract, may also be affected. However, isolated involvement of a single extramedullary organ is rarely seen in SM. We report on two patients with SM with splenic involvement, lack of 'diagnostic' mast cell (MC) infiltrates in the bone marrow, and absence of skin lesions. In one patient, a myelodysplastic syndrome was diagnosed prior to the detection of SM. Both patients presented with massive splenomegaly and multifocal MC infiltrates in splenic tissues. These MCs also expressed CD25 as well as the C-KIT mutation D816V. In consecutive examinations, the mutation was also detected in the bone marrow in both patients suggesting diffuse infiltration with neoplastic cells. In summary, our data show that the spleen can be a primary site of disease in rare cases of SM. Mastocytosis should therefore be considered as a (rare) differential diagnosis in patients with splenomegaly of unknown etiology.

Mastocytosis: pathology, genetics, and current options for therapy

Mast cell disorders are defined by an abnormal accumulation of tissue mast cells (MCs) in one or more organ systems. Symptoms in mastocytosis result from MC-derived mediators and, less frequently, from destructive infiltration of MCs. Cutaneous mastocytosis (CM) is a benign disease of the skin and may regress spontaneously. Systemic mastocytosis (SM) is a persistent disease in which a somatic c-kit mutation at codon 816 is usually detectable in MCs and their progenitors. The clinical course in these patients is variable ranging from asymptomatic for years to highly aggressive and rapidly devastating. The WHO discriminates five categories of SM: indolent SM (ISM), aggressive SM (ASM), SM with associated clonal hematological non-MC-lineage disease (AHNMD), and mast cell leukemia (MCL). The c-kit mutation D816V is quite common and may be found in all SM-categories. In SM-AHNMD, additional genetic abnormalities have been reported, whereas no additional defects are yet known for ASM or MCL. Patients with ISM and CM are treated with "mediator-targeting" drugs, whereas patients with ASM or MCL are candidates for cytoreductive therapy. The use of "Kit-targeting" tyrosine kinase inhibitors such as STI571 (Imatinib, Gleevec), has also been suggested. However, the D816V mutation of c-kit is associated with relative resistance against STI571. Therefore, these patients require alternative targeted drugs or new drug-combinations. In patients with SM-AHNMD, separate treatment plans for the SM-component and the AHNMD should be established. Examples include the use of STI571 in patients with SM plus hypereosinophilic syndrome (SM-HES) and the FIPL1/PDGFRA fusion gene target, or chemotherapy for eradication of AML in patients with SM-AML.

Indolent systemic mastocytosis with elevated serum tryptase, absence of skin lesions, and recurrent severe anaphylactoid episodes

BACKGROUND

In contrast to aggressive mastocytosis, patients with indolent systemic mastocytosis (ISM) usually present with urticaria pigmentosa-like skin lesions. In those who lack skin lesions, mastocytosis is often overlooked or confused with endocrinologic, allergic, or other internal disorders.

CASE REPORT AND RESULTS

We report on a 33-year-old male patient in whom severe hypotensive episodes occurred after contact with ants or yellow jackets. Since no specific IgE was detected, the serum tryptase concentration was measured and found to be clearly elevated (70 ng/ml). Consecutive staging and examination of the bone marrow revealed ISM. The patient was advised to circumvent insect contact, to take antihistamines on demand, and to carry an epinephrine self-injector for emergency events. In a retrospective analysis of 40 patients seen between 1988 and 2003, only 2 had a life-threatening mediator-related episode before ISM was diagnosed.

CONCLUSIONS

Our report confirms the diagnostic value of tryptase in patients with suspected mastocytosis. In addition, the report suggests that the lack of typical skin lesions does not exclude an indolent form of mastocytosis even if the serum tryptase is clearly elevated. Finally, our case further shows that mastocytosis can be an important differential diagnosis to be considered in patients with unexplained anaphylactoid or other mediator-related symptoms.

Granulocyte function in patients with L-ferritin iron-responsive element (IRE) 39C-->T-positive hereditary hyperferritinaemia-cataract syndrome

BACKGROUND

Hereditary hyperferritinaemia-cataract syndrome (HHCS) is an autosomal dominant trait associated with mutations in the iron responsive element (IRE) of the ferritin light-chain (L-ferritin) gene. Patients typically show elevated serum ferritin concentrations without iron overload and a bilateral cataract. Hyperferritinaemia can be associated with granulocyte dysfunction in patients with thalassemia beta and in haemodialysis patients. The effect of increased L-ferritin levels on granulocyte function in patients with HHCS is unknown.

MATERIAL AND METHODS

We examined glucose uptake, oxidative burst, chemotaxis, phagocytosis, apoptosis and intracellular calcium concentrations in polymorphonuclear leucocytes (PMNLs) of five affected members of a family with HHCS and in five healthy individuals matched for age and gender.

RESULTS

Mutation testing revealed a 39C-->T transition in IRE in all five patients with HHCS. Serum ferritin levels of patients ranged between 907 and 2030 microg L(-1), respectively. In comparison with healthy individuals, PMNLs of patients with HHCS showed a significant increase in PMA-mediated stimulation of the oxidative burst, as well as a significantly higher stimulation of glucose uptake but no difference with respect to chemotaxis, phagocytosis, apoptosis and intracellular calcium concentrations.

CONCLUSION

In summary, our study suggests that hyperferritinaemia in patients with IRE 39C-->T-positive HHCS is associated with activation of PMNLs but not with disturbance of fundamental PMNL function.

Numbers of colony-forming progenitors in patients with systemic mastocytosis: potential diagnostic implications and comparison with myeloproliferative disorders

BACKGROUND

An increase in colony-forming progenitor cells (CFU) is typically seen in myeloproliferative disorders (MPD). Systemic mastocytosis (SM) is a haemopoietic neoplasm involving myeloid progenitors similar to MPD. In the present study, we measured the levels of peripheral blood (pb) and bone marrow (bm) CFU in patients with different categories of SM, and compared them with those obtained in MPD patients and healthy controls.

MATERIALS AND METHODS

Numbers of CFU (CFU-GM, BFU-E, CFU-GEMM) were measured in a colony assay in 25 patients with SM [indolent SM (ISM), n = 15; smouldering SM (SSM), n = 3; SM with an associated haematologic clonal non-mast cell lineage disease (SM-AHNMD), n = 5; aggressive SM (ASM), n = 1; mast cell leukaemia (MCL), n = 1] and 37 with MPD [chronic myeloid leukaemia (CML), n = 10; polycythemia vera (PV), n = 8; essential thrombocytosis (ET), n = 9; idiopathic myelofibrosis (IMF), n = 10].

RESULTS

In the patients with MPD, elevated numbers of pb CFU were detected in all groups when compared with healthy controls (P < 0.05). In most of the patients with ISM, circulating CFU levels (CFU-GM, BFU-E, and CFU-GEMM) were within the normal range. In SSM, pb CFU-GM levels were normal in two patients, and elevated in a third patient. In the "SM-AHNMD-group", CFU levels were found to reflect the nature of the AHNMD: in SM with concomitant acute myeloid leukaemia (SM-AML, n = 2), the levels of CFU were low or undetectable, whereas in SM with chronic myelomonocytic leukaemia (SM-CMML, n = 2), elevated numbers of pb CFU-GM were found.

CONCLUSION

The numbers of CFU are normal in patients with ISM, but elevated in some patients with SSM and SM-CMML. An elevated CFU level in SM should raise the suspicion of an associated MPD (CMML) or smouldering SM, a novel SM-subtype that shares several features with MPD and sometimes progresses to an overt SM-MPD.

A case of smouldering mastocytosis with peripheral blood eosinophilia and lymphadenopathy

Systemic mastocytosis (SM) is a clonal hematologic disease showing abnormal growth and accumulation of mast cells (MC) in visceral organs with or without skin involvement. The clinical course in SM is variable. In fact, indolent and aggressive variants have been described. In addition, SM patients may acquire an associated hematologic clonal non-MC lineage disease (AHNMD). In some cases, hematologic parameters are indicative of slowly progressing SM although the clinical course remains indolent over years. These cases have been referred to as smouldering SM. We report on a smouldering patient presenting with typical skin lesions, hypercellular marrow with focal MC aggregates, persistent leukocytosis (20,000-30,000/microl) with eosinophilia (5-10%), marked lymphadenopathy, and splenomegaly. The C-KIT mutation Asp-816-Val confirmed the diagnosis of SM. The clinical picture remained stable during an observation period of 10 years without signs of progression to an AHNMD or a high grade MC disease. These data show that some patients with SM can remain in a clinically indolent smouldering state over years even when presenting with marked eosinophilia and lymphadenopathy.

Stem cell factor-induced bone marrow mast cell hyperplasia mimicking systemic mastocytosis (SM): histopathologic and morphologic evaluation with special reference to recently established SM-criteria

Although systemic mastocytosis (SM) is a well-defined hematologic neoplasm, it is sometimes difficult to discriminate between SM and a reactive mast cell (MC) hyperplasia. We describe a patient with aplastic anemia who was treated with recombinant stem cell factor (SCF). In response to SCF, the patient showed transient hematologic improvement and developed a marked increase in MC as well as a transient increase in serum tryptase. Histologic and immunohistochemical examination revealed a huge increase in MC in the bone marrow with focal infiltrates similar to SM. However, most of the SM-criteria were not met: First, MC showed normal cytomorphological characteristics without significant atypias (no cytoplasmic extensions, no oval nuclei, no hypogranulated cytoplasm). Furthermore, bone marrow MC were CD2- and CD25-negative and did not exhibit the C-KIT 2468 A-->T mutation (Asp-816-Val). After discontinuation of SCF the MC hyperplasia resolved confirming its reactive nature. Based on our case and similar cases mimicking mastocytosis, it seems of importance to apply recently established SM criteria in order to discriminate between reactive MC hyperplasia and true mastocytosis with certainty.

Increased prevalence of combined MTR and MTHFR genotypes among individuals with severely elevated total homocysteine plasma levels

The prevalence of the methionine synthase (MTR) 2756A-->G polymorphism among individuals with severely elevated total homocysteine (tHcy) plasma levels is unknown. Therefore, 1,716 subjects, including 415 hemodialysis patients, 179 peritoneal dialysis patients, 733 kidney graft recipients, and 389 healthy subjects, were investigated. The distribution of MTR 2756A-->G, as well as 5,10-methylenetetrahydrofolate reductase (MTHFR) 677C-->T/1298A-->C, genotypes among study participants with extremely high tHcy plasma levels (>90th percentile) was compared with the genotype distribution of subjects with very low tHcy plasma levels (<10th percentile). The prevalence of MTR 2756AG and GG genotypes alone did not differ between individuals with extremely high or extremely low tHcy levels (P = 0.7402; odds ratio [OR], 1.076; 95% confidence interval [CI], 0.697 to 1.662). Conversely, combined MTR and MTHFR genotypes (MTR 2756AG and 2756GG and MTHFR 677TT/1298AA and 677CT/1298AC) were found more often in the highest (n = 34) compared with the lowest plasma tHcy decile (n = 19; P = 0.0252; OR, 1.983; 95% CI, 1.079 to 3.643). The number of patients with the wild-type MTR and MTHFR genotype was three times greater in the lowest compared with the highest decile (17 versus 6 patients, respectively; P = 0.0155; OR, 0.330; 95% CI, 0.126 to 0.861). In summary, our study shows that the 2756A-->G transition of MTR in combination with MTHFR 677TT/1298AA and 677CT/1298AC can be associated with extremely high tHcy plasma levels.

A case of ‘smouldering’ mastocytosis with high mast cell burden, monoclonal myeloid cells, and C-KIT mutation Asp-816-Val

Mastocytosis is a term used for a group of disorders characterized by abnormal growth and accumulation of tissue mast cells (MC) in one or more organ systems. In patients with systemic mastocytosis (SM) the clinical course may be indolent or aggressive or even complicated by leukemic progression or an associated clonal hematologic non mast cell lineage disease (AHNMD). However, at first presentation (diagnosis) it may be difficult to define the category of disease and the prognosis. We report on a 48-year-old female patient with SM with urticaria pigmentosa-like skin lesions and mediator-related symptoms. She was found to have splenomegaly, a high infiltration grade (MC) in bone marrow biopsies (>30%), mild anemia, and a high serum tryptase level (>500 ng/ml). In addition, she exhibited discrete histologic signs of myeloproliferation in the 'non-affected' marrow and monoclonal blood cells established by C-KIT 2468A-->T mutation (Asp-816-Val) -analysis and HUMARA assay. Despite these findings, however, the clinical course was stable over years and no AHNMD or organ impairment developed. Because of the 'intermediate' clinical signs and absence of progression to aggressive disease, we proposed the term 'smouldering mastocytosis'.

Mutation analysis of C-KIT in patients with myelodysplastic syndromes without mastocytosis and cases of systemic mastocytosis

The proto-oncogene C-KIT encodes a tyrosine kinase receptor that is expressed on mast cells and haematopoietic stem cells and can show somatic mutations in patients with mastocytosis. Only scattered information is available about mutations in C-KIT in patients with other myeloid neoplasms. Moreover, the prevalence of mutations in C-KIT in bone marrow specimens of individuals with systemic mastocytosis is largely unknown. Using sequence analysis, we have screened cDNAs of the C-KIT domain encompassing codon 510-626 and codon 763-858 in bone marrow (BM) mononuclear cells (MNCs) of patients with myelodysplastic syndromes (n = 28) and patients with systemic mastocytosis (n = 12) for the presence of mutations. Furthermore, restriction fragment length polymorphism analysis was applied for identification of the C-KIT 2468A-->T and the C-KIT 1700T-->G mutation, as well as the C-KIT 1642A-->C polymorphism. All 11 patients with systemic indolent mastocytosis tested positive for C-KIT 2468A-->T. In contrast, no mutation was identified in the case of aggressive mastocytosis. Among patients with myelodysplastic syndromes, no patient showed a somatic mutation in C-KIT. The allele frequency for C-KIT 1642A-->C among the entire patient population was 0.038 and was 0.125 among age- and sex-matched healthy controls. Our data demonstrate that myelodysplastic syndromes without histological or cytological evidence of mastocytosis do not exhibit somatic mutations in exons 10, 11, 12, 16, 17 and 18 of C-KIT. In contrast, BM MNCs of patients with systemic indolent mastocytosis were all positive for C-KIT 2468A-->T and negative for additional mutations in these exons. The C-KIT 1642A-->C polymorphism is not associated with myelodysplastic syndrome or systemic mastocytosis.

Molecular analysis of the carboxy terminus of the beta and gamma subunits of the epithelial sodium channel in patients with end-stage renal disease

BACKGROUND

Mutations in the carboxy termini of the beta subunit (hbetaENaC) and the gamma subunit (hgammaENaC) of the human epithelial sodium channel have been identified in patients with Liddle syndrome. Moreover polymorphisms have been described in these genes, the clinical relevance of which for progression to end-stage renal disease (ESRD) is unknown. We, therefore, have screened ESRD patients for putative variants of these genes.

METHODS

We investigated 256 chronic hemodialysis patients, including 123 patients with a history of hypertension as a cause of ESRD. Screening for mutations in the carboxy termini of hbetaENaC and hgammaENaC was accomplished by polymerase chain reaction amplification followed by single-strand conformation polymorphism analysis.

RESULTS

In 231 patients single-strand conformation polymorphism analysis of the polymerase chain reaction fragments of the hbetaENaC and hgammaENaC genes showed a similar migration pattern as compared with negative control subjects. In 25 patients a band shift was observed. However, sequence analysis in all these patients revealed wild-type sequence.

CONCLUSIONS

The present study demonstrates the absence of genetic variants in the carboxy terminus of the hbetaENaC and hgammaENaC genes in Austrian patients with ESRD maintained on chronic hemodialysis treatment. Thus, mutations in these genes are unlikely to be associated with ESRD.

Erythropoietin-inducible immediate-early genes in human vascular endothelial cells

BACKGROUND

Patients receiving recombinant human erythropoietin (rHuEPO) may experience side effects arising from the vascular system. The underlying mechanisms, however, are largely unknown.

METHODS

To elucidate downstream events following erythropoietin receptor triggering, a differential display analysis of human vascular endothelial cell mRNA was performed.

RESULTS

We identified eight genes that were upregulated by rHuEPO as confirmed in two further independent cell culture experiments using a semiquantitative reverse transcriptase polymerase chain reaction (RT-PCR) protocol. The genes coded for proteins that may be assigned to four different groups: 1) proteins implicated in the regulation of vascular functions (thrombospondin-1, 20 kDa myosin regulatory light chain; relative increase of rHuEPO induced mRNA levels: 155.2%, P = 0.043; 137.6%, P = 0.046, respectively); 2) gene products involved in gene transcription and/or translation (c-myc purine-binding transcription factor PuF, tryptophanyl-tRNA synthetase, S19 ribosomal protein; increase of mRNA levels: 126.4%, P = 0.032; 150.9%, P = 0.012; 134.9%, P = 0.038); 3) subunits of mitochondrial enzymes related to energy transfer (NADH dehydrogenase subunit 6, cytochrome C oxidase subunit 1; increase of mRNA concentrations: 141.7%, P = 0.007; 140.3%, P = 0.01); and 4) regulators of signal transduction (protein tyrosine phosphatase G1, increase of transcript level: 160.3%, P = 0.016).

CONCLUSIONS

We report on novel molecular downstream events following rHuEPO receptor triggering of human vascular endothelial cells. We identified EPO-responsive immediate-early genes, coding for proteins involved in vascular functions, gene transcription, and/or translation, energy transfer, and signal transduction. Thus, our data provide new insights into the molecular changes induced by EPO in human vascular endothelial cells.

Systemic mastocytosis associated with acute myeloid leukaemia: report of two cases and detection of the c-kit mutation Asp-816 to Val

A subset of patients with systemic mastocytosis (SM) develop acute myeloid leukaemia (AML). However, little is known about the biology of such leukaemias and their relationship to the mast cell (MC) lineage. We report on two female patients who suffered from SM and AML. According to FAB criteria, the leukaemias were classified as AML-M4 (patient 1) and AML-MO (patient 2). The coexistence of the two distinct neoplasms (AML and SM) was demonstrable by immunostaining of serial bone marrow (BM) sections with monoclonal antibodies (mAb). In particular, the MC infiltrates were found to react with mAb against MC-tryptase and MC growth factor receptor c-kit (CD117), but not with mAb to CD15 or CD34. In contrast, the AML blasts were immunoreactive for CD15 (patient 1) or CD34 (patient 2), but did not express tryptase. The c-kit point mutation Asp-->Val at codon 816, considered to play a role in the transformation of MC progenitors, was detected in patient 1 in a BM cell fraction containing 4% MC. However, no c-kit mutation was found in pure AML blasts (<1% MC). These findings argue against an evolution of the AML clone from neoplastic MC or MC-committed progenitors.