Viral Load-based Evaluation of the Sensitivity of Antigen-based Rapid Detection Assay for SARS-CoV-2

Background: Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has become a global public health problem. The real-time reverse transcription-polymerase chain reaction (RT-PCR) is the gold standard test for the detection of SARS-CoV-2. However, the assay requires hours to get the final results. Therefore, antigen-based rapid assays are being used extensively to reduce the time. We have evaluated the performance of the antigen-based rapid test for the detection of SARS-CoV-2 virus in comparison with RT-PCR. Materials and methods: Nasopharyngeal and throat swabs were collected from 366 suspected patients of COVID-19 visiting our institute and subjected to qualitative RT-PCR and antigen-based rapid assays to detect the presence of SARS-CoV-2 virus. The sensitivity and specificity of the antigen-based assay were calculated in comparison with RT-PCR. Results: Compared with RT-PCR, sensitivity and specificity of the antigen-based rapid assay were observed to be 70.5% and 98.6%, respectively, in comparison with RT-PCR. However, the sensitivity of antigen-based rapid assay varied significantly with decreasing viral load. The sensitivity of the rapid antigen assay was equivalent to RT-PCR (23/23, 100%) at a higher viral load (Ct value 15�). In contrast, the antigen assay could only detect 3/21 (14.28%) samples with Ct value >30. Conclusion: The antigen-based assay could assist in the rapid screening of a large population. However, the rapid antigen assay might not detect early stages of infection represented by low viral load. Therefore, the antigen-based assay could not replace RT-PCR testing. The study reiterates that all antigen-based negative tests should be confirmed by RT-PCR.

Cytomorphological patterns in the Diagnosis of Tuberculous lymphadenitis.

The reliable diagnosis of tuberculous lymphadenitis by FNAC has important implications in a developing country like India. The aim is to study various cytomorphological patterns seen in tuberculous lymphadenitis and their correlation with AFB positivity. Fine needle aspiration cytology (FNAC) was performed on three hundred and twenty two patients with lymphadenopathy referred to the cytopathology section of pathology department, Sri Guru Ramdas Institute if Medical sciences and research Amritsar from August 2010 to July 2012. The patients with cytological diagnosis of tuberculous lymphadenitis were followed for their response to antitubercular treatment. A total of 322 FNACs were performed on patients with lymphnode lesions; out of which the most common (119) cytological diagnosis was tuberculous lymphadenitis. The most common pattern observed was (group II) presence of epitheloid granuloma with caseation necrosis which was seen in about half (50.5%) of the cases followed by smears with caseation necrosis only (group III) (27.7%) and smears with epitheloid granulomas only (group I) (21.8%).The overall AFB positivity was seen in 19.3% cases of tuberculous lymphadenitis. Maximum (30.3%) AFB positivity was seen in smears (group III) with only necrotic debris without granuloma and was least in group I (7.6%).While comparing Group I smears with that of group III using Fisher’s exact test, the difference in AFB positivity between the smears was statistically significant as the two-tailed p value was 0.0496. Thus FNAC is safe, easy, quick reliable as well as conclusive for the diagnosis of tuberculous lymphadenitis when done along with Zeihl Neelsen stain for acid fast bacilli.

Emerging influenza virus: a global threat.

Since 1918, in?uenza virus has been one of the major causes of morbidity and mortality, especially among young children. Though the commonly circulating strain of the virus is not virulent enough to cause mortality, the ability of the virus genome to mutate at a very high rate may lead to the emergence of a highly virulent strain that may become the cause of the next pandemic. Apart from the influenza virus strain circulating in humans (H1N1 and H3N2), the avian influenza H5N1 H7 and H9 virus strains have also been reported to have caused human infections, H5N1 H7 and H9 have shown their ability to cross the species barrier from birds to humans and further replicate in humans. This review addresses the biological and epidemiological aspects of influenza virus and efforts to have a control on the virus globally.

Tuberculosis presenting as osteolytic soft tissue swellings of skull in HIV positive patient: a case report.

We present a clinical case report of a 40-year old HIV positive male patient presenting with fever, cough with expectoration and osteolytic, cystic, multiple soft tissue swellings of skull (aspirate showing AFB). The various clinical possibilities are discussed along with interpretation of subsequent investigations.

Low prevalence of hepatitis B virus and hepatitis C virus co-infection in patients with human immunodeficiency virus in Northern India.

AIM: To study the prevalence of HBV and HCV co-infection in patients with HIV attending a referral hospital in Northern India. METHODS AND MATERIAL: The study cohort included six hundred and twenty consecutive HIV infected patients who were studied for co-infection with HBV/HCV or both. It included four hundred and seventy two male and one hundred and forty eight female patients between the age group 25-50 years. HBV and HCV infection was diagnosed by ELISA. Other routine investigations were also done. RESULTS: Out of a total of 620 consecutive HIV infected patients studied, HBV co-infection was detected in 14/ 620 (2.25%) patients and HCV co-infection in 10/620 (1.61%) patients and dual co-infection (HBV/HCV) in 1/620(0.16%). The mode of transmission of HBV was sexual contact in all (100%), while for HCV it was sexual contact in 5 patients (50%), blood transfusion in 4 patients (40%) and intravenous drug use (IDU) in 1 patient (10%). CONCLUSION: The prevalence of co-infection with HBV/HCV is much lower in our study population as compared to that reported in Western literature.

Evaluation of influenza virus detection by direct enzyme immunoassay (EIA) and conventional methods in asthmatic patients.

Throat gargle specimens of fifty-seven acute asthmatic patients (age range 18-40 years) were collected for the study. Thirty-four patients were found influenza virus positive in acute asthma cases. Influenza virus was isolated by conventional culture method on MDCK cell-line and by enzyme immunoassay test (EIA). The EIA negative specimens were retested after virus amplification on MDCK cell-line. Virus shedding and virus surface receptors assay was carried out to determine influenza virus titre. Airway functions were measured by spirometry. A good relationship was observed between the degree of airflow limitation and presence of influenza virus infection (p < 0.001; r = 0.85). A comparable difference in % FEV1 was observed in relation to the symptoms. The patients with greater viral antigen load had lower % FEV1. Two specimens, which were EIA negative, turned out to be positive after amplification on MDCK cell-line. The sensitivity was 98% and specificity was 100%. It was concluded that EIA method is a useful diagnostic tool as it detects influenza viral antigen quickly as compared to conventional methods.

Release of superoxide anion from activated mouse peritoneal macrophages during Mycobacterium tuberculosis infection.

Mouse peritoneal macrophage monolayers infected with M. tuberculosis were cultured in RPMI up to 7 days. Release of superoxide was assayed on different days in presence or absence of Phorbol myristate acetate (PMA), a known stimulator of NADPH oxidase which is involved superoxide production. Basal level of superoxide release was significantly higher in M. tuberculosis infected peritoneal mouse macrophages (P < 0.01) as compared to normal mouse macrophages. When normal and tuberculoid macrophage cultures were stimulated with PMA, increased superoxide anion release was observed in both the cultures but the increase of superoxide was significantly higher in normal macrophages as compared to tuberculoid stimulated macrophages. Superoxide release was maximum in 4 day old cultured macrophages and gradually it declined in older cultures by day 7, both in vitro and in vivo. A defective macrophage function in killing of M. tuberculosis bacilli was observed after 4 days of in vitro and in vivo cultures.

Effect of corticosteroid treatment on various serological & bronchoalveolar lavage abnormalities in patients with sarcoidosis.

Effect of daily oral prednisolone treatment was studied in 29 patients with pulmonary sarcoidosis. Twenty normal control subjects were also studied. Pretreatment absolute lymphocyte counts and proportion of lymphocytes in peripheral blood were significantly lower in patients with sarcoidosis as compared to normal controls. Total cell count and the proportion of lymphocytes in bronchoalveolar lavage (BAL) fluid were significantly higher in sarcoidosis. The proportion of CD3+ and CD4+ was significantly lower in peripheral blood and higher in BAL fluid in patients with sarcoidosis. Immunoglobulins (IgG, A and M) and complements (C3, C4 and CH50) were significantly higher both in peripheral blood and BAL fluid. Patients with sarcoidosis were treated with daily oral prednisolone (30 mg/day). Repeat studies were performed after an interval of 4-6 months in 20 patients with sarcoidosis. A significant increase in absolute lymphocyte counts in peripheral blood and decrease in the proportion of lymphocytes in BAL fluid occurred with prednisolone treatment. Proportion of CD3+, CD4+ and B cells increased in peripheral blood and decreased in BAL fluid. Complement and immunoglobulin levels revealed a significant reduction in peripheral blood and BAL fluid. It is concluded that patients with sarcoidosis have peripheral blood lymphopaenia and lymphocytic alveolitis. They have increased levels of complement and immunoglobulins both in the peripheral blood and BAL fluid. All these abnormalities show significant improvement with prednisolone treatment.

Immunologic & pulmonary function abnormalities in tropical pulmonary eosinophilia.

Twenty six patients (24 males and 2 females) with tropical pulmonary eosinophilia (TPE) were studied. Arterial blood gas analysis, pulmonary functions, peripheral blood examination and bronchoalveolar lavage (BAL) were performed. Peripheral blood and BAL fluid analyses were performed in healthy volunteers. Pulmonary functions revealed a mild restrictive ventilatory defect with airways obstruction. Mild hypoxaemia was observed on arterial blood gas analysis. Serum immunoglobulins IgG (P < 0.01), IgA (P < 0.001) and IgM (P < 0.001) were significantly raised as compared to normal controls. Serum complement (C3) level was higher, however, it was not significantly different as compared to normal controls. Serum haemolytic component of the complement (CH50) was significantly higher (P < 0.001) in patients with TPE compared to normal control subjects. The immunoglobulins IgG, IgA and IgM in the BAL fluid were significantly (P < 0.001) increased as compared to normal controls. The fibronectin (FN) level was also significantly increased (P < 0.001) in the BAL fluid. It is concluded that patients with TPE have mild restrictive ventilatory defect with airways obstruction and mild hypoxaemia. They have eosinophilic alveolitis with increased levels of immunoglobulins in the peripheral blood and BAL fluid. The significance of elevated FN in the BAL fluid is not clear and serial estimations may have to be done in order to clarify its role in the pathogenesis of fibrosis in chronic TPE.

Intrapulmonary vascular dilatations with hypoxemia in extrahepatic portal vein obstruction.

Several mechanisms have been suggested for the development of hypoxemia in cirrhosis. A few patients of portal hypertension due to non cirrhotic liver disease with cyanosis have also been reported earlier. We report probably the first documented case of portal hypertension with portal cavernoma and a normal liver, who had intrapulmonary vascular dilatations leading to hypoxemia and cyanosis. Our case suggests that changes leading to hypoxemia can occur due to portal hypertension alone, in the presence of a normal liver.

Colloidal bismuth subcitrate in non-ulcer dyspepsia.

The effect of colloidal bismuth subcitrate (De-Nol) on symptoms, Helicobacter pylori status and histological features was studied in 35 patients with non-ulcer dyspepsia. Pain (34 cases) and gas bloat (18) were the predominant symptoms. H pylori was present in 26 (74.3%) patients. Gastritis and duodenitis were present in 29 of 32 and 22 of 31 cases respectively in whom biopsies were available. Relief in symptoms after treatment was seen in 29 (82.8%) cases. Improvement in gastritis and duodenitis was noted in 60.8% and 58.8% respectively; over 70% of H pylori positive patients cleared the organism. These changes did not correlate with the relief in symptoms. We conclude that colloidal bismuth subcitrate is effective in the short term treatment of non-ulcer dyspepsia. It also clears H pylori infection and results in improvement of histological features.

Scintigraphic right-to-left liver lobe ratio and liver-to-spleen ratio in cirrhosis and non cirrhotic liver diseases.

Various criteria are used together for the scintigraphic diagnosis of cirrhosis as no single criterion may be reliable. However, low right-to-left hepatic lobe uptake ratio has been reported to be sensitive and specific for alcoholic cirrhosis. A low liver-to-spleen uptake ratio has also been reported in various hepatocellular disorders. We tested these ratios in patients with cirrhosis and non cirrhotic causes of portal hypertension. The right-to-left lobe uptake ratio was significantly lower (1.59 +/- 1.23 vs 2.36 +/- 0.63 in normals; p = 0.037) in only Child's C alcoholic cirrhosis, but the sensitivity of this ratio was low (40%) even in this subgroup of cirrhosis (mean +/- SD 1.72 +/- 1.08) as against 1 of 10 patients with non cirrhotic portal hypertension (3.57 +/- 1.33; p = 0.0005). We conclude that the right-to-left hepatic lobe uptake ratio is not a discriminatory scintigraphic sign in liver disease. A low liver-to-spleen uptake ratio can distinguish cirrhosis from non cirrhotic causes of portal hypertension.

Determinants of acid secretion.

Acid secretion is regulated by hormonal factors acting peripherally and centrally, as well as neural factors. Gastrin and histamine are the two most important peripheral hormonal stimulants, while the vagus is the predominant nerve affecting acid secretion. Meal related acid secretion occurs in three phases: cephalic, gastric and intestinal. Acid secretion is stimulated in the first two phases while it is inhibited in the intestinal phase. Proteins are potent acid stimulants but carbohydrates and fats are inhibitors. Tea, coffee, milk and alcohol are acid stimulants; on the other hand the damaging influence of spices on the stomach may not be related to increased acid secretion. Psychological stress has a variable effect. The effect of Helicobacter pylori infection on acid secretion is being elucidated. Many drugs modifying acid secretion are available and are useful in the treatment of acid peptic disease.

Evaluation of a modified medium for the one hour urease test for Helicobacter pylori infection.

The biopsy urease test is a simple and rapid method for the diagnosis of Helicobacter pylori infection; results are obtained within 4 h to 24 h. Various modifications of the media used in this test have been tried, to improve the accuracy and speed of the test. We compared the yield obtained with two media: the standard Christensen's urea medium and a modified plain urea medium (without the nutrients glucose and peptone); the result was read upto 1 h. In the first 53 cases, culture was obtained when either of the media gave a negative result. There was no difference in false positives in the two media, while there were more false negatives with the plain urea medium (4) compared to the Christensen's medium (1). In the latter 69 patients, we determined the accuracy of the two media by obtaining culture in all cases. The Christensen's medium had a sensitivity of 100% and a specificity of 92.1%, while the plain urea medium had a sensitivity of 96.7% and a specificity of 92.1%. The speed of reaction in both media was similar. We conclude that the Christensen's urea medium gives accurate results even when read at 1 h; the plain urea medium gives similar results.