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ORIGINAL ARTICLE
Year : 2023  |  Volume : 22  |  Issue : 1  |  Page : 40-44  

CO RADS grade of HRCT Thorax and RT PCR testing for the diagnosis of coronavirus disease 2019 (COVID 19): A descriptive hospital based study of asymptomatic planned surgery cases


1 Department of Medicine, Murshidabad Medical College, Murshidabad, India
2 Department of Anesthesiology, Murshidabad Medical College, Murshidabad, India
3 Central Sector Scheme for Promotion of AYUSH Interventions in Public Health Initiatives (PHI), Ministry of AYUSH, New Delhi, India
4 Department of Medicine, Nightingle Hospital, Kolkata, India
5 Department of Stroke Medicine, Worcestershire Acute Hospital NHS Trust, West Yorkshire, UK

Date of Submission23-Sep-2021
Date of Acceptance11-Dec-2021
Date of Web Publication24-Jan-2023

Correspondence Address:
Kaushik Ghosh
Flat No 401, Crystal Apartment, 14/1 Natun Para Road, Murshidabad, West Bengal
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/aam.aam_205_21

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   Abstract 


Background: The coronavirus disease 2019 (COVID-19) reporting and data system (CO-RADS) grade of high-resolution computed tomography (HRCT)–thorax scan investigation is an innovative tool for the diagnosis of COVID-19 patients. By this tool, majority of moderate-to-severe COVID-19 patients are screened to detect lung pathologies. Hardly any study has explored its use vis-a-vis reverse transcriptase-polymerase chain reaction (RT-PCR) in asymptomatic patients. Objectives: (1) The objective of the study is to assess the frequency COVID-19 patients among asymptomatic subjects who were admitted in the hospital for planned surgery, (2) estimate the sensitivity and specificity of CO-RADS grade of HRCT-thorax investigation for the diagnosis of COVID-19 patients where RT-PCR test was considered as “Gold Standard” test. Methodology: A descriptive retrospective study was conducted by studying the records in the case files of 150 patients who were admitted in the Department of General Surgery, Man Mohini Health Clinic, Murshidabad, West Bengal for minor surgical procedures between September 1 and December 31, 2020. Data were collected from hospital records. The CO-RADS grade of HRCT-thorax investigation and RT-PCR test were performed for the diagnosis of severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2) virus. The MS-excel application was applied for data analysis. Results: The mean age of the participants was 42.58 ± 14.29 years. A total of 17 (11%) and 39 (26%) of the patients were diagnosed with COVID-19 by HRCT-thorax and RT-PCR test, respectively. The sensitivity and specificity of CO-RADS grade of HRCT-thorax investigation for diagnosis of COVID-19 patients were 43.58% and 100%, respectively. The positive and negative predictive values of CO-RADS grade of HRCT-thorax investigation were 100% and 83.45%, respectively. Conclusions: The frequency of asymptomatic patients with COVID-19 that was missed by HRCT thorax was high, compared to the gold standard RT-PCR, reflecting its low sensitivity and low negative predictive value in the diagnosis of SARS-CoV-2 virus infection. Hence, it is difficult to conclude in favor of HRCT thorax as first-line screening modality in all individuals.

   Abstract in French 

Résumé
Contexte: Le système de notification et de données sur la maladie à coronavirus 2019 (COVID 19) (CO RADS) la tomographie (HRCT)–exploration du thorax est un outil innovant pour le diagnostic des patients COVID 19. Par cet outil, la majorité des Les patients COVID 19 modérés à sévères sont dépistés pour détecter les pathologies pulmonaires. Pratiquement aucune étude n'a exploré son utilisation vis-à-vis réaction en chaîne par transcriptase polymérase (RT PCR) chez des patients asymptomatiques. Objectifs: (1) L'objectif de l'étude est d'évaluer la fréquence Patients COVID 19 parmi les sujets asymptomatiques qui ont été admis à l'hôpital pour une chirurgie planifiée, (2) estimer la sensibilité et la spécificité de grade CO-RADS de l'investigation HRCT-thorax pour le diagnostic des patients COVID-19 où le test RT-PCR a été considéré comme “Gold Standard” test. Méthodologie: Une étude rétrospective descriptive a été menée en étudiant les dossiers des dossiers de 150 patients admis dans le département de chirurgie générale, clinique de santé Man Mohini, Murshidabad, Bengale occidental pour des interventions chirurgicales mineures entre septembre 1 et 31 décembre 2020. Les données ont été recueillies à partir des dossiers hospitaliers. Le grade CO RADS de l'examen HRCT thorax et du test RT PCR était réalisée pour le diagnostic du virus du coronavirus 2 lié au syndrome respiratoire aigu sévère (SRAS CoV 2). L'application MS Excel a été appliquée pour l'analyse des données. Résultats: L'âge moyen des participants était de 42,58 ± 14,29 ans. Au total, 17 (11 %) et 39 (26 %) des patients ont été diagnostiqués avec COVID 19 par HRCT thorax et test RT PCR, respectivement. La sensibilité et la spécificité du grade CO-RADS de l'investigation HRCT-thorax pour le diagnostic des patients COVID-19 étaient de 43,58 % et 100 %, respectivement. Les valeurs prédictives positives et négatives du grade CO RADS de L'investigation HRCT-thorax était de 100 % et 83,45 %, respectivement. Conclusions: La fréquence des patients asymptomatiques atteints de COVID 19 qui manqué par HRCT thorax était élevé, par rapport à la RT-PCR de référence, reflétant sa faible sensibilité et sa faible valeur prédictive négative dans le diagnostic d'infection par le virus SARS CoV 2. Par conséquent, il est difficile de conclure en faveur de HRCT thorax comme modalité de dépistage de première ligne chez tous les individus.
Mots-clés: personnes asymptomatiques, tomodensitométrie haute résolution - thorax, transcriptase inverse-réaction en chaîne par polymérase maladie à coronavirus 2019

Keywords: Asymptomatic persons, high-resolution computed tomography-thorax, reverse transcriptase-polymerase chain reaction coronavirus disease 2019


How to cite this article:
Ghosh K, Ghosh S, Acharyya A, Sarkar K, Bhattacharya A, Hassan MS, Ghosh US. CO RADS grade of HRCT Thorax and RT PCR testing for the diagnosis of coronavirus disease 2019 (COVID 19): A descriptive hospital based study of asymptomatic planned surgery cases. Ann Afr Med 2023;22:40-4

How to cite this URL:
Ghosh K, Ghosh S, Acharyya A, Sarkar K, Bhattacharya A, Hassan MS, Ghosh US. CO RADS grade of HRCT Thorax and RT PCR testing for the diagnosis of coronavirus disease 2019 (COVID 19): A descriptive hospital based study of asymptomatic planned surgery cases. Ann Afr Med [serial online] 2023 [cited 2023 Feb 1];22:40-4. Available from: https://www.annalsafrmed.org/text.asp?2023/22/1/40/368402




   Introduction Top


Since the very first case of coronavirus disease 2019 (COVID-19) in December 2019 when it was detected in Wuhan, China, the whole world has been facing the biggest pandemic since after the Spanish flu of 1918.[1] India is now facing the second wave of this pandemic sporadically. Till date (April 23, 2021) more than 10 million cases have been registered as per the Government of India's data with many more undocumented asymptomatic cases.[2]

During the period of data collection for this study, there was no official announcement of community transmission by the government. However, we have been noticing frequent diagnosis of asymptomatic COVID-19 cases in regular clinical practices of this study area.

The COVID-19 cases have been diagnosed as severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2) nucleic acid testing by reverse transcriptase-polymerase chain reaction (RT-PCR) results from nasopharyngeal swab. The sensitivity rate varies from 50 to 70%.[3],[4] The high false-negative rate initially stressed the role of high-resolution computed tomography (HRCT) scan of thorax in asymptomatic patients.[5] The definite computerized tomography (CT) changes are noted and scored based on the CT severity scoring CO-RAD was proposed by The Dutch Radiological Society.[6]

Various community surveys showed varied prevalence of COVID-19 positivity in different populations at different given points of time. However, there was hardly any data on the frequency of asymptomatic COVID-19-positive subjects diagnosed by HRCT-thorax investigation in the study area. This observational retrospective study has been conducted to document the frequency of COVID-19 cases who had visited the hospital for routine surgery and was completely asymptomatic on validated COVID-19 questionnaires. A further attempt was made to correlate HRCT scan of thorax in this patient population with RT-PCR results from nasopharyngeal swab.


   Methodology Top


A descriptive retrospective study was conducted among 150 participants, who were admitted in the Department of General Surgery, Manmohini Health Clinic, Murshidabad, West Bengal for minor surgical procedures between September 1 and December 31, 2020. The data were retrieved from hospital records based on the inclusion criteria of our study. The inclusion and exclusion criteria were as follow:

Inclusion criteria

  1. Only admitted asymptomatic COVID patients in the Department of General Surgery for any surgical procedure in this hospital within the study period
  2. None of the participants had any signs or symptoms suggesting of COVID-19 during admission
  3. None of them had been diagnosed with COVID-19 before admission.


Exclusion criteria

  1. Symptomatic COVID patients who were admitted in the Department of General Surgery within the study period
  2. Previously diagnosed COVID patients were not included.


After admission for surgery, all the 150 participants underwent RT-PCR test for the diagnosis and confirmation of SARS-CoV-2 virus infections as well as HRCT-thorax investigation for lung pathology.

As a routine practice in the hospital, few basic demographic and clinical information were collected from the patient relatives during admission procedure (from Voter Id/PAN/Aadhaar cards). Required data were collected from the patient's hospital records. To collect any missing information, the research team contacted the family members through telephone. The permission for the collection of information from hospital records was obtained from the hospital authority. The ethical clearance has been waved as it was a retrospective study.

CO-RADS grades were performed in suspected COVID-19 infection. The infection was graded from very low or CO-RADS 1 up to very high or CO-RADS 6, and the severity and stage of the disease were determined with remarks on comorbidity and differential diagnosis.

Statistical tests were performed in mean, standard deviation, range, and frequency using Microsoft Excel software. The cross-tabulation analysis was performed manually to find the sensitivity and specificity of the HRCT-Thorax test for the diagnosis of COVID-19.


   Results Top


A total of 150 patients were included in this retrospective study. Among them, 45 patients were diagnosed with COVID-19 by any one of the above-mentioned tests. A total of 17 (11%) and 39 (26%) of the patients were diagnosed with COVID-19 by HRCT-thorax investigation and RT-PCR test, respectively [Table 1].
Table 1: Demographic characteristics and test reports (n=150)

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The mean age of the participants was 42.58 ± 14.29 years with age range of 17–79 years. There were more females 96 (64%) than males 54 (36%) [Table 1].

Summary of [Table 2]: High-resolution computed tomography-chest investigation for diagnosis of coronavirus disease 2019
Table 2: High-resolution computed tomography-thorax test report and reverse transcription-polymerase chain reaction test report in cross-tabulation

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  1. Sensitivity: 43.58% (43.58% COVID-19 patient screened by HRCT-Thorax test will give true-positive result and the remaining 56.42% a false negative result)
  2. Specificity: 100% (100% of the non-COVID-19 patients screened by HRCT-Thorax test will give true-negative result and 0% of non–COVID-19 patients will be wrongly classified as COVID-19 when they are not)
  3. False negative: 56.4%
  4. False positive: 0%
  5. Predictive value of a positive test: 100% (Only 100% of patients with positive HRCT-thorax test for COVID-19 result really have COVID-19; the remaining 0% have false-positive result)
  6. Predictive value of a negative test: 83.45% (only 83.45% of patients with negative HRCT-thorax test for COVID-19 result really does not have COVID-19; the remaining 16.55% have false-negative result).



   Discussion Top


The preoperative screening for COVID-19 infection in elective surgical patients is done routinely during the COVID-19 pandemic for the safety of both health-care workers and patients. These patients are at high risk of peri and postoperative complications as well as increase risk of spread of infection in the hospital community by the asymptomatic COVID-19-positive patients. In this article, we are discussing the observational findings of COVID-19 diagnosis by HRCT–thorax and RT-PCR tests among asymptomatic planned operative patients in a rural hospital of West Bengal.

A total of 17 (11%) and 39 (26%) patients were diagnosed with COVID-19 by HRCT-Chest investigation and RT-PCR test, respectively [Table 2]. This number is quite alarming and this positivity rate is comparatively higher than national data.[7] However, Integrated Disease Surveillance Programme documented 80% COVID-19 patients are asymptomatic in India till August 23, 2020.[8]

Till date, a consensus is yet to be reached about COVID-19 screening by HRCT thorax or RT-PCR test for COVID-19 detection. The HRCT thorax test is costly and resource challenged. The specificity and sensitivity of RT-PCR test for the detection of novel coronavirus among symptomatic COVID patients have been reported from 68% to 100% and 92% to 100%, respectively.[9] The Centre for diseases control and prevention reported that RT-PCR test accuracy was lower (sensitivity 41.2% and specificity 98.4%) when used for screening of asymptomatic persons.[10] This discrepancy between reported sensitivity of diagnosis of COVID-19 infection by RT-PCR among asymptomatic patients and necessity of early detection of pulmonary involvement by HRCT thorax has provided liberty to health-care workers to develop their own safety protocol.

HRCT thorax is a conventional, noninvasive imaging option with relatively rapid high accuracy. A time-demand diagnostic criterion on CT features has been developed in CORADS classification [Table 3].
Table 3: Coronavirus disease 2019 reporting and data system score (level of suspicious for coronavirus disease 2019)[6],[11]

Click here to view


In our study, we had chosen the subjects who were healthy in terms of COVID features as initial clinical and validated COVID-19 questionnaires completion. The patients underwent simultaneous RT-PCR testing for COVID-19 as well as HRCT thorax for screening as per CO-RAD classification on the same day of appointment.

In several studies in recent days, HRCT thorax is done in RT-PCR negative patients to determine the sensitivity of HRCT thorax in comparison with RT-PCR.[12] The data of this study were collected at the time when the Ministry of Health and Family Welfare of India had not reported any community transmission of the COVID-19 virus. In spite that, we observed a substantive number of asymptomatic COVID-19-infected patients during routine screening activity by HRTC-thorax and RT-PCR test. As per the British Society of Thoracic Imaging, CO-RAD score 3 onward on the HRCT finding is corresponding to Classic COVID-19 level of confidence more than 70%.[11] Accordingly, CO-RAD 3 onward on the HRCT findings has been taken for identification of suspicious COVID patients. A comparison between RT-PCR testing and HRCT thorax findings showed sensitivity and specificity of HRCT thorax is 43.58% and 100%, respectively. It is also observed that 22 (15%) of patients diagnosed by RT-PCR with COVID-19 were not diagnosed by HRCT-Thorax CO-RAD grading. This finding may be due to the absence of lung pathology in CT scan report.

One meta-analysis on chest CT for the detection of COVID-19 concluded that Chest CT offered great sensitivity for detecting COVID-19, especially in a region with severe epidemic situations. However, the specificity was reported low. In the context of emergency disease control, chest CT provides a fast, convenient, and effective method for early detection of suspicious cases and might contribute to confine epidemic.[13] However, a definite conclusion was difficult from the meta-analysis as most of the studies lacked good sample size and patients were mostly moderate to severely symptomatic. Our study strictly included only asymptomatic persons and subjects whose screening was part of a routine pre-operative protocol rather than treatment itself.

In view of low specificity of HRCT thorax, the American College of Radiology discourages routine use of this imaging modality for screening purposes.[14] However, in view of circumstantial evidence and supporting clinical features, HRCT thorax can be used even as first-line investigation modality to initiate early categorization of severity and place of treatment. Our study yields a relatively high specificity of HRCT thorax in asymptomatic patients. The low sensitivity of HRCT thorax in this study may be due to the absence of lung pathology in some COVID-19-positive asymptomatic patients.

Ganta et al.[15] reported 100% correlation between RTPCR testing and HRCT thorax positivity in their study. We found only 100% and 83.45% positive and negative predictive values, respectively, for HRCT–Thorax. It means 100% of patients with positive HRCT Thorax test for COVID-19 result really had COVID-19, whereas 83.45% of patients with negative HRCT-Thorax test for COVID-19 result really did not have COVID-19; the remaining 16.55% of the study subjects had false-negative results.

In this descriptive retrospective study with the findings of low sensitivity for HRCT thorax in asymptomatic COVID patients, it is difficult to conclude in favor of HRCT thorax as a first-line screening modality in all individuals. However, in the time of an ongoing COVID pandemic, when ARDS is the leading cause of death, the physician may introduce HRCT thorax as an initial screening modality for patients who are high risk. More studies are needed to be conducted to further validate this recommendation.

Limitation

Being a retrospective study, the number of cases that could be included was quite limited and randomization was not implemented in the sampling procedure. Potential causes of CT imaging errors, such as the CT partial volume effect, could not be ascertained, as well as the bias of patient's own reporting on COVID-19 infection due to social stigma and health inertia. The participants of this study were mainly preoperative patients, so the study findings may not be generalized to the general population. Further prospective study with large sample size after removing all the limitations as listed above will help in making more meaningful conclusions.


   Conclusions Top


There was very high frequency of asymptomatic COVID-19-positive patients in our study population. Low sensitivity with high specificity and high positive predictive values for the diagnosis of COVID-19 were observed in the HRCT-Thorax scan test of our patients. Hence, it is difficult to conclude in favor of HRCT thorax as first-line screening modality in all individuals in our environment. Further large sample size prospective studies are required to validate our recommendations.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
   References Top

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Ganta R, Kantharia SR, Shah BB, Vasava RM, Vaishnav TV, Kantharia RA. Role of HRCT thorax in pre operative assessment of RT PCR COVID 19 negative oral cancer patients. J Radiol Oncol 2020;4:008-11.  Back to cited text no. 15
    



 
 
    Tables

  [Table 1], [Table 2], [Table 3]



 

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