Table 3.

Antibody titer and CT results of 4 patients whose N protein is consistently negative.

Patient ID	Marker	1–3 days after admission	4–6 days after admission	7–9 days after admission	>9 days after admission
3	Antibody titer	Negative	Negative	1:1*	1:1*
	CT imaging	A little inflammation under the pleura of the right lower lobe and under pleura of the left upper lobe	A little inflammation under the pleura of the right lower lobe and in the upper left lung	A little inflammation of the left lung	A little inflammation of the left lung
32	Antibody titer	Negative	Negative	1:1*	1:1*
	CT imaging	A little inflammation in the right upper lobe and left lower lobe	A little inflammation in the right upper lobe and left lower lobe, improved from previous exam	A little inflammation in the right upper lobe and left lower lobe, improved from previous exam	A little inflammation in the right upper lobe and left lower lobe, improved from previous exam
33	Antibody titer	1:1*	1:1*	1:1*	1:1*
	CT imaging	No obvious lesions in both lungs	No obvious lesions in both lungs	No obvious lesions in both lungs	No obvious lesions in both lungs
40	Antibody titer	Negative	Negative	Negative	Negative
	CT imaging	A little inflammation of the left upper lobe	A little inflammation of the left upper lobe, improved from the previous exam	A little inflammation of the left upper lobe, improved from the previous exam	A little inflammation of the left upper lobe, improved from the previous exam

1:1 *means when the serum is tested as undiluted, it showed weak positive results. Further dilution would result in negative reading.