COVID-19 pneumonia: Relationship between initial chest X-rays and laboratory findings

Abstract

Objective: To analyze the initial findings in chest X-rays of patients with RT-PCR positive for SARS-CoV-2, and to determine whether there is a relationship between the severity of these findings and the clinical and laboratory findings.

Materials and methods: This retrospective study analyzed the relationship between initial chest X-rays and initial laboratory tests in symptomatic adults with nasopharyngeal RT-PCR results positive for SARS-CoV-2 seen at our center between February 29 and March 23, 2020. Among other radiologic findings, we analyzed ground-glass opacities, consolidations, linear opacities, and pleural effusion. We also used a scale of radiologic severity to assess the distribution and extent of these findings. Among initial laboratory findings, we analyzed leukocytes, lymphocytes, platelets, neutrophil-to-lymphocyte ratio, and C-reactive protein.

Results: Of 761 symptomatic patients, 639 (84%) required hospitalization and 122 were discharged to their homes. The need for admission increased with increasing scores on the scale of radiologic severity. The extent of initial lung involvement was significantly associated with the laboratory parameters analyzed (P<.05 for platelets, P<.01 for lymphocytes, and P<.001 for the remaining parameters), as well as with the time from the onset of symptoms (P<.001).

Conclusion: It can be useful to use a scale of radiologic severity to classify chest X-ray findings in diagnosing patients with COVID-19, because the greater the radiologic severity, the greater the need for hospitalization and the greater the alteration in laboratory parameters.

Keywords: COVID-19; Chest radiography; Laboratory findings; Puntuación radiográfica; Radiografía de tórax; Radiographic score; Resultados de laboratorio; SARS-CoV-2.

Figure 1

Of the 1165 initial patients, four patients under 18 years of age were excluded. Another 165 patients were excluded because they did not have a chest X-ray taken at the onset of their disease, and 116 more patients were excluded as they did not have initial blood testing done. Finally, of the 880 remaining patients, 119 lacked laboratory testing corresponding to all five values required for inclusion in this study: leukocyte count, lymphocyte count, platelet count, lymphocyte-to-leukocyte ratio and CRP.

Figure 2

Chest X-ray with lung division into six fields used in our study to assess distribution of X-ray findings. The upper horizontal line is at the lower edge of the aortic arch and the lower horizontal line is at the height of the inferior pulmonary veins. A and B) Upper fields. C and D) Middle fields. E and F) Lower fields.

Figure 3

Percentage relationship between days elapsed since the onset of symptoms and X-ray severity score. The x-axis represents each X-ray severity score (scores 5 and 6 were combined due to limited numbers of patients). The y-axis represents the percentage of patients with a particular time since the onset of symptoms within each severity score.

Figure 4

A and B) A 49-year-old man, a former smoker who quit smoking five years earlier, had a history of hypertension, dyslipidaemia, hypertensive cardiomyopathy, hyperuricaemia, kidney transplantation and total thyroidectomy due to papillary thyroid carcinoma. He came in with fever, dry cough and muscle pain for the past four days. Laboratory data: leukocytes 7100/μl, lymphocytes 600/μl (lymphocyte-to-leukocyte ratio 7.7%), platelets 140,000/μl, CRP 1.63 mg/dl, D-dimer 754 ng/mL and LDH 471 U/l. A posteroanterior chest X-ray taken on 16 March 2020 showed a peripheral ground-glass opacity in the right middle field (X-ray severity score = 1) (arrow). The patient was admitted, and a chest X-ray taken on 24 March 2020 showed clear radiological worsening with more extensive bilateral lung consolidations (arrows) associated with an increased need for oxygen therapy. C and D) A 33-year-old woman from Guatemala with no personal history of note visited the accident and emergency department with a referral from her primary care doctor due to cough and fever for the past nine days. Blood testing: leukocytes 5100/μl, lymphocytes 1400/μl (lymphocyte-to-leukocyte ratio 27.9%), platelets 224,000/μl, CRP 8.44 mg/dl, D-dimer 500 ng/mL and LDH 666 U/l. A posteroanterior chest X-ray taken on 17 March 2020 identified patchy bilateral lung consolidations predominantly in the lower lobes (score = 5) (arrows). The patient was admitted, and two days later, she showed worsening of signs and symptoms as well as laboratory values; a chest X-ray taken on 23 March showed radiological worsening, with confluence of her prior consolidations.