Results of a Quality Improvement Program for Sweat Testing to Diagnose Cystic Fibrosis

Abstract

ScienceAlthough mandatory newborn screening throughout the United States for cystic fibrosis (CF) has resulted in increased sweat chloride testing for infants, obtaining an adequate volume of sweat to perform this test has remained a challenge. Currently, the standard as established by the National Clinical and Laboratory Standards Institute (NCCLS) for patients older than 3 months is to achieve a less than 5% quantity not sufficient rate (QNS) rate. 1 Nonetheless, studies 2-4 examining QNS rates at various health care centers show significant variability, with data published from accredited CF centers 2 demonstrating QNS rates as high as 19% for infants older than 3 months. For infants who may undergo a sweat test at age 3 months or younger as part of a newborn and infant screening program, QNS rates are higher, with a value of 32.8% reported in one study. 3 Recently, a goal of less than 10% QNS was suggested for infants undergoing sweat testing as part of newborn screening. 2,3 Further, although several consensus statements and guidelines 2-4 detail ways to achieve lower QNS rates, data that demonstrate results achievable via a comprehensive quality improvement (QI) effort are lacking.Screening of newborns for CF using the dried-blood spot 2-tiered immunoreactive trypsinogen/DNA method began in 2008 in the state of Illinois. All positive screening results require subsequent sweat chloride testing. 5 The Cystic Fibrosis Center of Chicago (CFCC) at St. Alexius Medical Center (SAMC) was selected as one of the designated newborn screening centers for the state of Illinois for sweat testing. The laboratory at SAMC is accredited by the College of American Pathologists (CAP) and for implementing the newborn and infant screening program at the CFCC at SAMC. Clinical and Laboratory Standards Institute (CLSI) guidelines for sweat testing 1 were closely followed and several technicians were selected to perform this test. After an initial testing period, reevaluation and development of an ongoing QI program for sweat testing were instituted to improve the QNS rates in all age groups. MethodsAll sweat tests were performed by pilocarpine iontophoresis via the Macroduct coil sweat collection system (Wescor, Logan, UT) and quantitatively analyzed for chloride concentration using a digital coulometric chloridometer (LabConco, Kansas, MO). All tests from the beginning of the program in Abstract Background: Obtaining an adequate volume of sweat to measure chloride is a challenge for many cystic fibrosis centers. The standard for patients older than 3 months is a less than 5% quantity not sufficient (QNS) rate; the suggested goal for patients aged 3 months or younger is a less than 10% QNS rate. St. Alexius Medical Center (SAMC) began performing sweat chloride testing in 2008. After an initial period of testing, a quality improvement (QI) program for sweat testing was instituted to improve QNS rates.

Improving the Rate of Sufficient Sweat Collected in Infants Referred for Sweat Testing in Michigan

“…Three of the 4 centers did not include analysis of QNS rate by technician performing the test similar to Boas et al 15 However, we were able to identify common problems between centers, which were addressed through conference calls and site visits. The sweat testing procedure was reviewed at every visit and necessary changes were implemented.…”

Newborn Screening for Cystic Fibrosis: Infant and Laboratory Factors Affecting Successful Sweat Test Completion

“…Current CFF guidelines suggest ST may be completed within the first 2 weeks of life (but greater than 24 h of age) in infants with BW >2.0 kg [ 16 ]. Despite these suggestions, many States have documented QNS rates >10% despite guidelines provided by the CFF [ 25 , 26 , 27 ]. Over 2 years, the average ST QNS rate at our CF Center was 22% but fluctuated depending on interventions and decreased to an average of 14% in the last 6 months of the study when addressing infant and laboratory factors.…”

“…Similarly, ST completion was limited to 3 days/week. Fluctuations in ST success/QNS rates highlight the importance of ongoing QI measures between the CF center and clinical laboratory staff to sustain best practices and investigate areas for future improvement [ 26 ].…”