Longitudinal Assessment of Diagnostic Test Performance Over the Course of Acute SARS-CoV-2 Infection.

BACKGROUND: Serial screening is critical for restricting spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) by facilitating timely identification of infected individuals to interrupt transmission. Variation in sensitivity of different diagnostic tests at different stages of infection has not been well documented. METHODS: In a longitudinal study of 43 adults newly infected with SARS-CoV-2, all provided daily saliva and nasal swabs for quantitative reverse transcription polymerase chain reaction (RT-qPCR), Quidel SARS Sofia antigen fluorescent immunoassay (FIA), and live virus culture. RESULTS: Both RT-qPCR and Quidel SARS Sofia antigen FIA peaked in sensitivity during the period in which live virus was detected in nasal swabs, but sensitivity of RT-qPCR tests rose more rapidly prior to this period. We also found that serial testing multiple times per week increases the sensitivity of antigen tests. CONCLUSIONS: RT-qPCR tests are more effective than antigen tests at identifying infected individuals prior to or early during the infectious period and thus for minimizing forward transmission (given timely results reporting). All tests showed >98% sensitivity for identifying infected individuals if used at least every 3 days. Daily screening using antigen tests can achieve approximately 90% sensitivity for identifying infected individuals while they are viral culture positive.

Longitudinal assessment of diagnostic test performance over the course of acute SARS-CoV-2 infection.

WHAT IS ALREADY KNOWN ABOUT THIS TOPIC?: Diagnostic tests and sample types for SARS-CoV-2 vary in sensitivity across the infection period. WHAT IS ADDED BY THIS REPORT?: We show that both RTqPCR (from nasal swab and saliva) and the Quidel SARS Sofia FIA rapid antigen tests peak in sensitivity during the period in which live virus can be detected in nasal swabs, but that the sensitivity of RTqPCR tests rises more rapidly in the pre-infectious period. We also use empirical data to estimate the sensitivities of RTqPCR and antigen tests as a function of testing frequency. WHAT ARE THE IMPLICATIONS FOR PUBLIC HEALTH PRACTICE?: RTqPCR tests will be more effective than rapid antigen tests at identifying infected individuals prior to or early during the infectious period and thus for minimizing forward transmission (provided results reporting is timely). All modalities, including rapid antigen tests, showed >94% sensitivity to detect infection if used at least twice per week. Regular surveillance/screening using rapid antigen tests 2-3 times per week can be an effective strategy to achieve high sensitivity (>95%) for identifying infected individuals.

Collection of the BD SurePath Pap Test with a broom device plus endocervical brush improves disease detection when compared to the broom device alone or the spatula plus endocervical brush combination.

OBJECTIVE: Here we examine the diagnostic utility of the US Food And Drug Administration (FDA) approved Spatula + endocervical brush combination for the BD SurePath Pap Test (SPPT) and compare it to SPPT collection with the broom alone or to an off-label combination of broom + EC brush. This question is important due to lingering concerns over the value of EC detection to a satisfactory Pap test. METHODS: 20,125 SPPT vials were examined for the collection devices contained. The SPPT collection device combinations allowed were: Rovers Cervex-Brush (broom, FDA approved), Medscand Pap Perfect Spatula + Medscand CytoBrush Plus GT (spatula + GT brush, FDA approved) or Rovers Cervex-Brush + Surgipath C-E Brush (broom + CE brush, off label). RESULTS: Examination of SPPT vials revealed 11,130 collected with the broom, 4,687 collected with the spatula + GT brush and 2,921 collected with the broom + CE brush. Absence of an endocervical/transformation zone was seen in 22.86% of broom cases, 13.10% of spatula + GT brush cases (p= 0.00005 vs broom) and 10.17% of broom + CE brush cases (p= 0.00005 vs broom, p= 0.00005 vs spatula + GT brush). Importantly, LSIL detection was: broom 2.99%; spatula + GT brush 2.45% (p= 0.053 vs broom); broom + CE brush 4.18% (p= 0.034 vs broom, p= 0.0001 vs spatula + GT brush). CONCLUSION: When broom + brush combination is compared to broom alone or to spatula + GT brush, the broom + CE brush combination better sampled the endocervical/transformation zone and increased LSIL detection.

Effectiveness of the SurePath liquid-based Pap test in automated screening and in detection of HSIL.

We have shown that SurePath when compared to conventional Paps fails to increase HSIL detection. In this study, assessment of test performance characteristics for the FocalPoint showed that sensitivity was 96% when manual screening was used as the "gold standard." When cervical biopsy, however, was used as the "gold standard" FocalPoint sensitivity decreased to 93%, which was the same as manual screening. Examination of the FocalPoint "no further review" cases showed that 4/296 were SIL. To understand better the implication of an SIL diagnosis, cervical biopsies generated from SurePath and conventional Paps were compared. Conventional Paps diagnosed as LSIL had a biopsy LSIL:HSIL ratio of 3.1/1, while SurePath Paps had a biopsy LSIL:HSIL ratio of 1.5/1. These results indicate that when cervical biopsy is used as the "gold standard," FocalPoint and manual screening of SurePath Paps have similar test performance but that the FocalPoint can fail to detect LSIL. Importantly, LSIL in a SurePath Pap is 1.6 times more likely to be HSIL on biopsy than LSIL in a conventional Pap.