(73) Decreasing Sweat Test QNS Percent Rates at Atrium Health CF Center: QI work always in progress

Background: Determination of sweat chloride (SwCl) concentration by pilocarpine iontophoresis continues to be the gold standard study for diagnosis of CF [1]. Testing consists of 3 steps: stimulation, collection and analysis of sweat sample. Minimal volumes or previously weights of sweat are required for an accurate SwCl determination [1]. Quantity Not Sufficient (QNS) samples are frustrating to patients and families, lab personnel and ordering providers and necessitate repeating the study. The Cystic Fibrosis Foundation (CFF) has determined minimal standards for QNS percent rates for patients 7 weeks to 4 months of < 10% and ≥ 4 months of < 5%. Recent data suggests that QNS percent rates for patients 2-6 weeks should be < 10% [2]. In 2017 we set out to improve our QNS percent rates to meet or exceed these standards.

Methods: Utilizing PDSA cycles and ongoing CF Center Director (Ctr Dir) involvement, we initiated multiple interventions to reduce our QNS percent rates over a 5-year period (figure). In 2017, the Ct Dir meet with Sweat Test Lab personnel and discussed importance of sweat testing, initiated monthly meeting with supervisors and lab personnel and monthly review of SwCl results for each age group. Also, SwCl Techs were retrained, and number increased from 2 to 3. In 2018, family PreVisit phone calls were initiated to ensure adequate patient preparation, SwCl Lab methodology was reviewed, annual competencies were updated with addition of knowledge assessment and supervisors rewrote Sweat Test Policy and Procedure Manual. In 2019, the new MacroDuct Collection System was purchased, and deep dives were made by Ctr Dir and team into each QNS occurrence. In 2020, 2^nd MacroDuct Collection System was purchased as backup, skills testing was added to annual competencies, 2020 CFF Virtual QI Consortium recommendations were reviewed and a Follow the Procedure Exactly policy with documentation of collection steps and review and correction of deviations was initiated. In 2021, SwCl collection transitioned to the new Pulmonary Diagnostic Lab with oversight by a new respiratory therapist lab director, onsite training by a MacroDuct representative occurred and PreVisit phone call information was reviewed & updated.

Results: From 2017-2021, annual QNS percent rates significantly improved and exceeded CFF minimal standards (see figure). We observed that monthly QNS percent rates varied significantly depending upon how many sweat tests were performed for each group. Monthly review and deep dives into QNS rates are important, but monthly QNS rates do not necessarily reflect improvement or deficit.

Conclusions: Improvement of SwCl QNS percent rates requires ongoing QI work and is always in progress. Important factors involved in improvement include Ctr Dir involvement, buy-in from persons collecting sweat samples, adequately preparing patients and families, following the sweat test procedure exactly every time and monthly review of results with deep dives into QNS occurrences.

Acknowledgements:

References: [1]. Ferrell PM, Rosenstein BJ, White TB, et al. Guidelines for diagnosis of cystic fibrosis in newborns through older adults: Cystic Fibrosis Foundation Consensus Report. J Pediatr 2008; 153 (2): S4-S14.

[2]. McColley SA, Elbert A, Wu R, et al. Quantity not sufficient rates and delays in sweat testing in US infants with cystic fibrosis. Pediatr Pulmonol 2020; 55(11): 3053-3056.