{"doi":"10.1101/2020.10.25.20219048","title":"Ct threshold values, a proxy for viral load in community SARS-CoV-2 cases, demonstrate wide variation across populations and over time","abstract":"ABSTRACT Information on SARS-CoV-2 in representative community surveillance is limited, particularly cycle threshold (Ct) values (a proxy for viral load). Of 3,312,159 nose and throat swabs taken 26-April-2020 to 13-March-2021 in the UK’s national COVID-19 Infection Survey, 27,902(0.83%) were RT-PCR-positive, 10,317(37%), 11,012(40%) and 6,550(23%) for 3, 2 or 1 of the N, S and ORF1ab genes respectively, with median Ct=29.2 (∼215 copies/ml; IQR Ct=21.9-32.8, 14-56,400 copies/ml). Independent predictors of lower Cts (i.e. higher viral load) included self-reported symptoms and more genes detected, with at most small effects of sex, ethnicity and age. Single-gene positives almost invariably had Ct>30, but Cts varied widely in triple-gene positives, including without symptoms. Population-level Cts changed over time, with declining Ct preceding increasing SARS-CoV-2 positivity. Of 6,189 participants with IgG S-antibody tests post-first RT-PCR-positive, 4,808(78%) were ever antibody-positive; Cts were significantly higher in those remaining antibody-negative. Community SARS-CoV-2 Ct values could be a useful epidemiological early-warning indicator. IMPACT STATEMENT Ct values from SARS-CoV-2 RT-PCR tests vary widely and over calendar time. They have the potential to be used more broadly in public testing programmes as an “early-warning” system for shifts in infectious load and hence transmission.","journal":"medRxiv","year":2020,"id":118896,"datarank":2.372973174705683,"base_score":3.6109179126442243,"endowment":3.6109179126442243,"self_citation_contribution":0.5416376868966337,"citation_network_contribution":1.831335487809049,"self_endowment_contribution":0.5416376868966337,"citer_contribution":1.831335487809049,"corpus_percentile":91.00332637116114,"corpus_rank":1164,"citation_count":36,"citer_count":29,"citers_with_citation_signal":23,"citers_with_endowment":23,"datacite_reuse_total":0,"is_dataset":true,"is_dataset_confidence":0.5799,"is_data_producer":false,"deposit_databanks":null,"is_oa":true,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"2020-01-01","fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":245227,"name":"Emma Pritchard","orcid":"0000-0002-0963-9260","position":1,"is_corresponding":false},{"id":245226,"name":"Thomas House","orcid":"0000-0001-5835-8062","position":2,"is_corresponding":false},{"id":245228,"name":"Julie V. Robotham","orcid":"0000-0003-2515-4084","position":3,"is_corresponding":false},{"id":245229,"name":"Paul Birrell","orcid":"0000-0001-8131-4893","position":4,"is_corresponding":false},{"id":248250,"name":"Iain Bell","orcid":null,"position":5,"is_corresponding":false},{"id":245232,"name":"John I. Bell","orcid":"0000-0003-4071-6460","position":6,"is_corresponding":false},{"id":23192,"name":"John Newton","orcid":"0000-0002-5641-6457","position":7,"is_corresponding":false},{"id":17597,"name":"Jeremy Farrar","orcid":"0000-0002-2700-623X","position":8,"is_corresponding":false},{"id":245233,"name":"Ian Diamond","orcid":"0000-0003-3069-7112","position":9,"is_corresponding":false},{"id":248288,"name":"Ruth Studley","orcid":null,"position":10,"is_corresponding":false},{"id":245250,"name":"Jodie Hay","orcid":"0000-0002-2000-2578","position":11,"is_corresponding":false},{"id":245230,"name":"Karina-Doris Vihta","orcid":"0000-0002-4111-7577","position":12,"is_corresponding":false},{"id":245237,"name":"Tim Peto","orcid":"0000-0003-3477-8307","position":13,"is_corresponding":false},{"id":245238,"name":"Nicole Stoesser","orcid":"0000-0002-4508-7969","position":14,"is_corresponding":false},{"id":245236,"name":"Philippa C. Matthews","orcid":"0000-0002-4036-4269","position":15,"is_corresponding":false},{"id":245248,"name":"David W. Eyre","orcid":"0000-0001-5095-6367","position":16,"is_corresponding":false},{"id":245225,"name":"Koen B. Pouwels","orcid":"0000-0001-7097-8950","position":17,"is_corresponding":false},{"id":553237,"name":"the COVID-19 Infection Survey team","orcid":null,"position":18,"is_corresponding":false},{"id":245234,"name":"A. Sarah Walker","orcid":"0000-0002-0412-8509","position":0,"is_corresponding":true}],"reference_count":37,"raw_metadata":null,"created_at":"2026-07-18T23:14:03.409507Z","pmid":null,"pmcid":null,"fwci":null,"citation_percentile":null,"influential_citations":0,"oa_status":null,"license":null,"views":0,"total_file_size_bytes":0,"version_count":0,"fair_f":null,"fair_a":null,"fair_i":null,"fair_r":null,"fair_zscore":null,"fair_rationale":null,"fair_model":null,"fair_agent_version":null,"fair_fulltext_source":null,"fair_has_llm":null,"fair_computed_at":null,"clinical_trials":[],"software_tools":[],"db_accessions":[],"linked_datasets":[],"topics":[]}