3.2. Description of Studies and Study Characteristics
The 15 studies that passed all eligibility criteria came out between
1900 and 2020 (Table 1); 12 of the studies were published in
English12,30,42,43,34–41, two of them published in
Chinese10,44, and one published in
Spanish1, including 5 studies in KTP
group10,30,34,35,44 and 10 articles in
CO2 group1,12,36–43. These studies
totally involved 612 patients with LP and 2120 surgeries treated with
CO2 laser/KTP laser, including 102 KTP cases and 510
CO2 cases separately. There are 8 retrospective
studies1,12,36–38,40,42,43 with only 2 prospective
works39,41 in CO2 group, while KTP
group contains 2 retrospective10,44 and 3 prospective
studies30,34,35. Besides, the patient population
selected in studies is different and most studies recruited patients
with recurrent laryngeal/respiratory papillomatosis, while others
included inverted papilloma30, laryngeal
papilloma1,38,42,44, juvenile-onset
RRP39 (Table 1). All studies included males and
females with a higher percentage of males (Mele: 65.61% and 66.25% for
KTP and CO2 respectively), and there was no differences
between the gender percentages of the two groups (p>0.05) (Table 2).
However, significant difference existed between the average age of KTP
and CO2 group (p<0.001) before surgery (Table 2).
Besides, sample sizes ranged between 3 and 244 (median 39).
Specifically, the sample sizes for the CO2 group and KTP
group were 3-222 and 9-39, respectively. The evidence levels of all the
studies were classified as level D. All studies accessed samples from
outpatient departments.