Table 2:

Causes of polycythemia, hypoalbuminemia and hypotension and the reasons for exclusion in our patient

Presentation	Differential diagnosis	Reason for exclusion
Polycythemia
Primary polycythemia	Inherited: Congenital heart defects	Normal transthoracic echocardiogram
	Acquired: Polycythemia vera	Absence of Janus kinase 2 (JAK-2) mutation (Val671Phe)
	Leukemia	Absence of BCR-ABL t(9;22) mutation
Secondary polycythemia	Chronic hypoxia or cardiopulmonary abnormalities	No clinical symptoms of obstructive sleep apnea and low risk according to the STOP-BANG score No known chronic pulmonary disease No obesity hypoventilation syndrome and no daytime hypercapnia No elevation of erythropoietin level: 4.6 (normal range 5.0–16.0) IU/L Normal hemoglobin and hematocrit levels between acute episodes No history of high-altitude travel
Secondary polycythemia	Erythropoietin-secreting tumours	Level of erythropoietin not high
Relative polycythemia	Dehydration Capillary leak syndrome	Not excluded
Hypoalbuminemia	Nephrotic syndrome	No proteinuria, negative urine protein-to-creatinine ratio: undetectable (normal < 0.15 g protein/g creatinine) No evidence of hyperlipidemia that may be associated with nephrotic syndrome (normal fasting lipid profile)
	Poor nutrition or liver cirrhosis	Rapid correction of serum albumin levels is inconsistent with hypoalbuminemia from poor nutrition or cirrhosis No features of liver cirrhosis or ascites on abdominal CT
Hypotension and shock	Sepsis	Normal procalcitonin level 0.28 (normal 0.00–0.39) μg/L and C-reactive protein level 4.9 (normal 0.0–10.0) mg/L No evidence of infection on chest radiography and abdominal CT Two negative results for blood cultures Negative result for urine culture Negative result for screening (RT–PCR) test for SARS-CoV-2 (COVID-19 direct diagnostic kit) Negative result for serology screening test for SARS-CoV-2 IgG Negative results for screening for common respiratory viruses and pathogens: syncytial respiratory virus; influenza type A (H1 and H3); influenza type B; parainfluenza viruses 1, 2, 3 and 4; human metapneumovirus; entero-rhinovirus, coronavirus NL 63, HKU1, OC43 and 229E; adenovirus; Bordetella pertussis and parapertussis; Chlamydophilia pneumoniae; or Mycoplasma pneumoniae Negative results for serology screening test for HIV-1 and -2 (p24 combo)
	Cardiogenic and obstructive shock	Normal FAST ultrasonography in the emergency department Normal electrocardiogram Normal transthoracic echocardiography and negative result for exercise stress test (recent outpatient investigations) Absence of pulmonary edema and raised central venous pressure Normal cardiac enzymes (troponin < 3 [normal 0–18] ng/L) and D-dimer levels (353 [normal < 500] μg/L) Negative V/Q
	Anaphylaxis	Absence of typical clinical signs or symptoms associated with anaphylaxis (e.g., respiratory compromise, rash, pruritus, angioedema or persistent gastrointestinal symptoms) Normal tryptase level: 3.0 (normal < 11) μg/L
	Hereditary angioedema	Normal C4 esterase activity (0.20 [normal 0.13–0.40] g/L) and C1 esterase activity (0.97 [normal 0.69–1.42] g/L)
Other diseases excluded	Cancer drug reactions Hemophagocytic lymphohistiocytosis Viral hemorrhagic fever Snakebite envenomation	Absence of the epidemiologic factors usually associated with these diagnoses

Note: CT = computed tomography, FAST = focussed assessment with sonography for trauma, IgG = immunoglobulin G, RT–PCR = reverse transcription–polymerase chain reaction.