Methods
This study was a retrospective analysis of adult and pediatric CF patients aged 12 and above at the University of Iowa who received treatment with triple combination therapy for a year. It was approved by the Institutional Review Board. The study period was from November 2019, when the FDA approved TCT, until April 2021.
Patients included in the study had a confirmed diagnosis of CF, were on TCT, had a recorded weight within six months of TCT therapy, and had a follow-up visit approximately a year after initiation of TCT.
We excluded participants with CF-related metabolic syndrome, not on the TCT, those who did not return to the clinic for follow-up appointments, patients taken off medication one year after initiation, patients transplanted within the first year of TCT initiation, or those who were pregnant at the time of TCT initiation.
Variables studied include age at initiation, gender, race and ethnicity, CF mutations, and previous modulator taken by the subject, if applicable. Additionally, we identified the presence of pancreatic insufficiency, cystic fibrosis-related diabetes (CFRD) -identified by their use of chronic insulin-; gastroesophageal reflux disease (GERD) -identified by their use of proton pump inhibitors or H2 antagonists-. Nutritional supplementation and type (oral versus tube feeds) were also noted.
Baseline visits within six months prior to TCT initiation were captured, and the start date of TCT was used to identify follow-up visits approximately 3, 6, 9, and 12 (±3) months later. Only visits in which participants were clinically stable were chosen to represent baseline visits. Discharge from hospitalization data points was not used as baseline visits; in these cases, the prior clinic visit during which the patient was stable was chosen to represent baseline as long as it was within six months of initiation. For each visit, height, weight, and FEV1 were recorded. BMI percentile was calculated for patients under 20 years old using the ”CDC BMI Percentile Calculator for Child and Teen” 18 to account for continual growth. BMI was calculated for patients 20 years old and above by dividing weight (kg) by height (meter) squared. FEV1 percent predicted values were calculated using the ”Global Lung Function Initiative calculator for Spirometry” 19. As they turned 20 between baseline and the post-one-year follow-up visit, five additional patients were excluded, so their BMI percentile could not be calculated at the follow-up visit. Any hospitalizations between the baseline and 12-month follow-up visits were captured, along with the length of stay and admission reasons.
The primary aim of this study was to assess the weight change in CF patients after 12 months of initiating TCT; a secondary aim was to identify potential contributing factors that may promote weight gain in combination with highly effective modulator therapy such as TCT.
The change in BMI or BMI percentile at 12 months from TCT initiation was calculated for all patients included in the analysis. A Wilcoxon signed-rank test was used to compare pre-and-post-TCT BMI or BMI percentile. We conducted the analysis using SAS version 9.4 (SAS Institute, Inc., Cary, NC). P -values less than 0.05 were considered statistically significant.