Results
After searching all of the prior
mentioned databases, we came up with a total of 661 retrieved results.
Of these, 282 were duplicates and were thus removed. After the initial
screening of the remaining 379 articles, 67 articles were eligible to
enter the full-text screening process. Finally, following the careful
implementation of the inclusion/exclusion criteria mentioned above, we
encountered 16 eligible articles to enter the study. The schematic view
of the study selection process is provided in Figure 1 .
Cohorts accounted for the most
observed type of articles in our study, with 14 included papers. one
cross-sectional and one case-control study were also eligible to enter
this systematic review. All the data reported in the articles are
gathered from three distinct countries of China (14 articles), South
Korea (1 article), and Brunei (1 article) (Figure 2 ). Two
studies from South Korea provided the whole country’s data using
official South Korean governmental statistics (South Korea Center for
Disease Control and Prevention). Therefore, we excluded the study with
the smaller population due to their high possibility of population
overlap (Figure 1 ).
The details of the included
studies are discussed in Table 1 . The included articles yield a
total of 10,475 studied individuals. Of these participants, a sum of 489
(4.67%) patients were considered to be re-positive cases
(Figure 3 ).
Considering the articles reporting
gender prevalence, the overall population sums up to 1275 patients,
including 695 (54.51%) females and 580 (45.49%) males. Among the
studies reporting gender prevalence of both re-positive and
non-re-positive subgroups, total females and total males are 405/723
(56.02%) and 318/723 (43.98%), respectively. In the re-positive
subgroup, the female and male numbers are 50/88 (56.82%) and 38/88
(43.18%), sequentially. In the non-re-positive subgroup, females and
males account for 355/635 (55.91%) and 280/635 (44.09%) of the
population (Figure 4 ).
To understand the mean age of
different groups, we combined the studies that published the age data
for total, re-positive, and non-re-positive groups. The mean age for the
total population, the re-positive subgroup, and the non-re-positive
subgroup were 47.5 ± 16.9, 50.0 ±
18.0, and 46.6 ± 17.1, respectively.
Other than the details presented in Table 1 , PCR conversion
time (days between symptom onset to first negative PCR test), hospital
stays (days) during the first hospitalization, days between last
negative test and first re-positive PCR, second-time clinically
symptomatic patients among re-positive patients, second-time clinical
symptoms, comorbidities, days to second negative PCR, second-time chest
CT changes among re-positive patients, number of re-positives infecting
close contacts, number of re-positive patients with positive IgM and
IgG, number of non-re-positive patients with positive IgM and IgG, and
mean/median IgM and IgG levels for the included articles are
demonstrated in Supplementary Table 1 .
Combining all studies which reported symptom status among re-positive
cases, the rate of symptom presentation upon second positive test turned
out to be 20.0%. Among those, observed symptoms included cough
(68.2%), fever (31.8%), throat pain (9.1%), fatigue (22.7%), chest
discomfort (4.5%), chest expectoration (4.5%), itchy throat (4.5%)
and constipation (4.5%).
The most common comorbidities in re-positive patients according to
available data were hypertension (15.9%), diabetes (3.2%),
cerebrovascular disease (3.2%), depression (3.2%), tuberculosis in
mediastinal lymph nodes (1.6%), hepatopathy (1.6%), chronic
lymphocytic leukemia (1.6%), and pregnancy (1.6%).
Two studies reported the average number of days from second positive to
second negative, being 2.73 ± 2.03 (25) and 1.83 ± 0.22 (26) (combined
mean = 2.32 ± 1.56). The only re-positive patient in Qiao et al.’s study
(27) stayed in the hospital for approximately 17 days after her second
admission.
When comparing CT scans obtained upon first discharge and second
positive PCR of a total of 46 patients, thirteen (28.3%) showed no
improvement of lesions since initial discharge, while in the other 33
patients (71.7%), CT lesions were resolved to some extent.
Out of 64 patients whose antibody data were available, 55 (85.9%) had
positive IgG and 35 (54.7%) had positive IgM titers, based on each
study’s definition of “positive”. Some of the studies had also
gathered antibody information of their non-re-positive patients. When
combining available data, 93.9% of non-re-positive patients had
positive IgG profile, showing a significant difference with that of
re-positive patients (85.9%, p = 0.03), while 53.5% were positive for
IgM, which is not statistically different to that of re-positive
patients (54.7%, p = 0.86).