ABSTRACT
PURPOSE: Real time reverse transcriptase PCR (rRT PCR) although gold standard test for the diagnosis of SARS CoV-2, carries disadvantages of a sophisticated set up, long time to results and centralized services. The rapid antigen tests (RAT) can be used as a primary screening tool with the advantages of rapid turnaround time and ease of use. The study was conducted to determine the performance of rapid antigen test (standard Q COVID 19 Ag) in comparison to rRT PCR in symptomatic patients and asymptomatic contacts and asymptomatic patients with no apparent contact history. METHODS: Nasopharyngeal swabs taken in duplicate from 1034 patients were collected over a 5 months period. These included 248 (23.98%) symptomatic, 386 (37.34%) asymptomatic contacts and 400 (38.68%) asymptomatic subjects who were routinely screened in pre-operative period, as a prerequisite for travel, or pregnant females. Both rRT PCR and RAT were performed as per manufacturers' instructions. Performance of test in different subgroups of patients was evaluated. Performance of RAT test on basis of duration of illness and Ct values was also analyzed. RESULTS: In this study, 445 (43.04%) were rRT PCR positive, out of which 374 samples were RAT positive as well. 31 samples were RAT positive but PCR negative. The sensitivity, specificity, PPV and NPV of the rapid antigen test was 84.04%, 94.74%, 92.35% and 88.71% respectively. The negative predictive value of the test in asymptomatic patients without any significant contact history was 97.07%. CONCLUSIONS: This study recommends the use of the antigen test as a method of diagnosis for SARS CoV-2. However a negative result with RAT in suspected patients and their contacts should be viewed with caution. This study also finds the utility of using RAT test in the community settings as a screening test in schools, colleges and mass gatherings.
Subject(s)
COVID-19 , SARS-CoV-2 , COVID-19/diagnosis , COVID-19 Testing , Female , Humans , Nucleic Acid Amplification Techniques , Pandemics , SARS-CoV-2/genetics , Sensitivity and SpecificityABSTRACT
Increasing frequency of methicillin resistant Staphylococcus aureus infections and changing patterns in antimicrobial resistance have led to renewed interest in the use of macrolidelincosamide-streptogramin antibiotics. However therapy may fail either due to constitutive or inducible resistance. This study was undertaken to detect different phenotypes including inducible clindamycin resistance in clinical isolates of Staphylococcus aureus and coagulase negative Staphylococcus. Four hundred sixty five Staphylococcus aureus and 84 coagulase negative Staphylococci isolated from different clinical specimens were included in the study. On routine susceptibility testing plate clindamycin (2 microg) disk was placed at a distance of 15mm towards the centre from a peripherally placed erythromycin (15 microg) disk. Fisher exact test was used for statistical analysis. Out of 465 Staphylococcus aureus isolates, 237 (50.96%) were methicillin sensitive (MSSA) and 228 (49.03%) methicillin resistant (MLS(B)c).Over all 118 (25.37%) isolates showed constitutive resistance (MLS(B)c), 70 (15.05%) inducible clindamycin resistance, 143 (30.75%) MS(B) phenotype and 134 (28.81%) were susceptible to both erythromycin as well as clindamycin. Constitutive and inducible resistance to clindamycin were significantly higher in MRSA than MSSA (P=0.0000 and 0.0001 respectively). Out of 84 isolates of coagulase negative Staphylococci, 43 (51.19%) were methicillin sensitive (MSCNS) and 41(48.80%) methicillin resistant (MRCNS). Constitutive MLS(B) resistance was detected in 32 (38.09%), inducible clindamycin resistance 10 (11.90%), MS(B) phenotype 27 (32.14%) and 15 (17.85%) were susceptible to both erythromycin and clindamycin. Performing D test on a routine susceptibility plate saves material, manpower and time as inducible resistance can be reported simultaneously along with other susceptibility results.
