Cystic Fibrosis StripAssay

The Viennalab CF StripAssay is a qualitative assay for the targeted analysis of the most common mutations in the CFTR gene, the gene that encodes the cystic fibrosis transmembrane conductance regulator. Reference sequence NM_000492.3.

Clinical background

Cystic fibrosis is caused by variants in CFTR, a chloride channel in the epithelial cell membrane. Loss of function thickens the secretions of the lungs, the pancreas and other organs. The diagnosis rests on the clinical picture, the sweat test and genetic confirmation; genotyping is also used for carrier testing in family members and in reproductive counselling.

The four configurations

Each configuration has its own panel, so the mutation count differs. EXT covers 38 mutations, STD 34, GER 31 and TUR 24. In STD, TUR and EXT the IVS8 polyT variants 5T, 7T and 9T are reported separately from that count; the GER panel does not include them. The choice between configurations follows the population the laboratory serves. The IFU of the EXT configuration adds that DNA isolation methods other than the supplied procedure have not been validated for it.

Method and sample

The PCR is set up in two tubes, with Amplification Mix A and Amplification Mix B, and each sample is read on two strips: Teststrips A and Teststrips B, ten of each per pack. Biotinylated products are hybridised to allele-specific probes immobilised as parallel lines, detected with streptavidin-alkaline phosphatase and a colour substrate, and read by eye against the supplied Collector sheet. Every strip carries a control line for the PCR reaction and a hybridisation control; a no-template control is prepared by the user.

DNA extracted from EDTA blood, fresh or frozen, or from dried blood spots is used. The kit contains the lysis solution, GENxTRACT resin and HS-Taq DNA Polymerase (125 U). For DNA from another extraction system, 2 to 10 ng/µl with an A260/280 ratio of 1.7 to 2.0 is specified; ViennaLab also offers the GENxTRACT Blood DNA Extraction System (REF 2-014).

• Lysis Solution (50 ml)
• GENxTRACT Resin (5 ml)
• Amplification Mix A (yellow cap, 250 µl)
• Amplification Mix B (green cap, 250 µl)
• Taq Dilution Buffer (transparent cap, 500 µl)
• HS-Taq DNA Polymerase (5 U/µl, red cap, 125 U)
• DNAT (blue cap, 1.5 ml)
• Typing Trays (3)
• Teststrips A (black cap, 10)
• Teststrips B (white cap, 10)
• Hybridization Buffer (white cap, 25 ml)
• Wash Solution A (white cap, 80 ml)
• Conjugate Solution (transparent cap, 25 ml)
• Wash Solution B (transparent cap, 80 ml)
• Color Developer (brown cap, 25 ml)
• Instructions For Use (1)
• Collector Sheet (1)

Contents per configuration: REF 4-410 (STD), 4-420 (TUR), 4-430 (GER) and 4-440 (EXT). The controls are the control line and the hybridization control on each teststrip; a no-template control is prepared by the user. No separate control DNA is supplied. DNA extraction reagents beyond the lysis solution and resin are not supplied; ViennaLab recommends the GENxTRACT Blood DNA Extraction System (REF 2-014), which is ordered separately.