Decreasing the lower limit of quantitation (LLOQ) for the urine albumin-to-creatinine ratio (uACR) from 12 mg/L to 3 mg/L is analytically acceptable, clinically useful, and allows for interpretation of results for a significant percentage of samples that would otherwise be flagged as potentially abnormal, a recent paper reported (J Appl Lab Med 2022; doi: 10.1093/jalm/jfac046).

Clinicians use uACR to screen for chronic kidney disease (CKD). A value of more than 30 mg/g is considered abnormal, but lower ratios have prognostic implications. The researchers reason that urine albumin (uAlb) should be measurable to 3 mg/L to match the lowest creatinine concentration generally utilized (10 mg/dL) and maximize diagnostic utility. Meanwhile, most uAlb assays have lower limits of quantitation (LLOQs) 2- to 4-fold higher.

To determine the performance characteristics of a commonly used urine albumin assay at 3 mg/L and to evaluate the clinical screening impact of reducing the LLOQ, the researchers serially diluted urine to assess urine albumin linearity and precision for concentrations near the claimed LLOQ of 12 mg/dL. The researchers compared 30 samples with uAlb between laboratories and evaluated 1,239 sequential samples for clinical impact of reducing the measuring range to 3 mg/L.

The assay was linear to 1.6 mg/L. Interday precision at 3.7 mg/L and 4.3 mg/L was 7.7% and 8.6%, respectively. Minimal bias was observed between labs. Clinical validation demonstrated that 40.4% of the 1,239 samples had urine albumin less than 12 mg/L. Using 11.9 mg/L as the numerator for samples with uAlb less than 12 mg/dL and urine creatinine more than 10 mg/L, 21.4% of samples would have a ratio flagged abnormal at more than 30 mg/g. Reducing the numeric value for these samples to 3 mg/L reduced alarm to less than 1%.

The researchers noted that the newly suggested lower LLOQ provides clinical information for prognostic tools developed for people at risk for CKD.

Genomic Sequencing Aids Hearing Loss Detection in Ailing Newborns

Expanded genomic sequencing combined with hearing screening may effectively detect hearing loss among neonatal intensive care unit (NICU) patients, new research suggests (JAMA Netw Open 2022; doi:10.1001/jamanetworkopen.2022.20986).

Hearing loss is a global burden. Studies have indicated that newborns admitted to the NICU are thought to be at high risk, comprising 1.2% to 7.5% of cases of hearing loss. Meanwhile, NICUs employ different protocols for hearing screening.

Previous studies have shown that state newborn screening programs miss about 25% of hearing loss cases in infants, and two-thirds of affected babies go on to receive a diagnosis of severe to profound hearing loss. Other research indicates that hearing loss among newborns in the NICU is associated with genetic factors as well as clinical factors such as cytomegalovirus infection, craniofacial malformation, family history of hearing loss, duration of NICU stay, oxygen exposure, or low birth weight.

To assess the association between expanded genomic sequencing combined with hearing screening and detection of hearing loss in the NICU, the researchers studied 8,078 newborns admitted to the ICU of a children’s hospital in Shanghai. The researchers administered a hearing screening test and expanded genomic sequencing targeting 2,742 genes in each infant. Infants who failed the hearing screening test or had positive genetic findings were referred for diagnostic audiometry at a median of 3 months of age.

Among the infants, 21.7% received a diagnosis of hearing loss. Expanded genomic sequencing combined with hearing screening was associated with a 15.6% increase in cases of diagnosed hearing loss that hearing screening alone missed. Of the 52 patients with hearing loss, genetic factors were identified for 75%. The most commonly involved genes were GJB2 and SLC26A4. Patients with genetic findings experienced a more severe degree of hearing loss than those without genetic findings and had more bilateral hearing loss.

Test Shows Source of SARS-CoV-2 Immunity

A new whole blood test shows whether cellular immunity to SARS-CoV-2 results from vaccination or infection within 48 hours (Allergy 2022; doi: 10.1111/all.15406). The test uses type 2 cytokine IL-13 as a T-cellular recall marker for SARS-CoV-2-specific T-cellular immune responses.

Available antibody-based tests can measure SARS-CoV-2-specific immune response, but faster T cell assays that do not require specialized labs and many days turnaround time are needed to differentiate specific cellular immune responses after infection.

The researchers evaluated immune responses in whole blood among 117 individuals from three groups: those recovering from COVID-19, vaccinated subjects, and healthy controls. Responses included those from Th1, Th2, and Th17 cells, plus inflammatory cytokines.

The researchers also evaluated blood samples for activation-induced marker expression via incubated purified peripheral blood mononuclear cells, SARS-CoV-2 S, N, or M peptides, tetanus toxoid, tick-borne encephalitis virus and vaccine antigens, or polyclonal stimuli including Staphylococcal enterotoxin and phytohemagglutinin.

They found that N-peptide mix stimulation of whole blood showed the combination of IL-2 and IL-13 secretion was superior to IFN-γ secretion for discriminating between COVID-19-convalescent patients and healthy controls.

The researchers got comparable results with M- and S-peptides. S-peptides almost comparably recalled IL-2, IFN-γ, and IL-13 responses in whole blood of vaccinated participants.

Analysis of T cell response 10 months after infection revealed that the T cell response was still as strong as that measured 10 weeks after an infection. Whole blood cytokine responses correlated with cytokine and proliferation responses of peripheral blood mononuclear cells.

Antigen-induced neoexpression of the C-type lectin CD69 on CD4+ and CD8+ T cells gave the best information about SARS-CoV-2 exposure status, with additional benefit from CD25 upregulation.

The researchers believe that the test would be useful for determining presence and degree of T-cellular memory in patients with impaired or masked humoral immunity. This could help identify patients at risk of becoming reservoirs for developing variants of concern due to their inability to efficiently clear virus, as has been shown previously.

In addition, the researchers noted that the test’s speedier 2-day turnaround time could help clinicians in outpatient clinics and improve understanding of the development of T cell-mediated SARS-CoV-2 immunity.