Find out more at www.alphalabs.co.uk/FIT 11 Which FIT's Best? Guildford Medical Device Evaluation Centre (GMEC) Evaluation of Quantitative Faecal Immunochemical Tests for Haemoglobin The excellent clinical outcome data demonstrated in many publications, require faecal haemoglobin cut-offs for referral for further investigation, at the low end of the analytical range of the available FIT systems. The choice of laboratory method is therefore important to the objective evaluation of patients, not only for haemoglobin stability in the specimen collection device, but also for its low bias and small imprecision at the lower limit of the analytical working range. Four FIT analytical systems were evaluated by the Guildford Medical Device Evaluation Centre (GMEC) in 2013. The resulting report is available online: http://194.97.148.137/assets/downloads/pdf/ activities/fit_reports/gmec_fit_evaluation_ report.pdf Extracts of data from that report are represented here. In this study, the HM-JACKarc system, supplied by Alpha Laboratories, was described as one of the more precise methods (Table 1). Its analytical working range correlated well to the expected values of spiked faecal samples. The ability to detect haemoglobin at both the lower and higher limits of the analytical range was confirmed (Figure 1). HM-JACKarc demonstrated a high sensitivity with a lower limit of detection of just 0.6 µg Hb/g faeces, making it ideal for symptomatic testing (Table 2). In addition, sample stability was proven at 20C throughout the 30 day period of the study (Table 3). Confirmed by GMEC: ■ Stability of sample in the collection tube claims of the pack insert • 120 days at 4-8°C • 14 days at 25°C ■ The Hook capacity greater than 200,000 µg of Hb / g faeces ■ Linearity across the measurement range (7-400 µg of Hb / g faeces) ■ Described as very sensitive at the low end with LOD as 0.6 µg of Hb / g faeces Table 2. HM-JACKarc Sensitivity Measured lower limit of detection for each analyser. Quoted lower limits of detection were provided by each manufacturer in their data sheets. Mean concentration of 20 un-spiked collection tubes (µg Hb/g faeces) Standard deviation Lower limit of detection (µg Hb/g faeces) Quoted lower limit of detection (µg Hb/g faeces) HM-JACKarc 0.3 0.1 0.6 7 NS-PLUS C15 0.0 0.0 0.0 4 OC-SENSOR DIANA 2.1 0.9 3.8 10 FOB Gold/BioMajesty 0.5 0.4 1.3 2.55 Table 1. HM-JACKarc Precision Imprecision measured against manufacturers’ mean concentrations Buffer Samples GMEC data mean sr Manufacturer data Consistent/ not consistent with claim σ mean σr Verification value HM-JACKarc (µg Hb/ g faeces) 13.5 0.9 11.3 0.6 0.9 NSD 58.8 1.3 56.1 2.4 3.5 Consistent 319.4 5.4 279.5 7.9 11.6 Consistent KEY: sr – GMEC measured estimate of repeatability σr – manufacturers’ claimed repeatability NSD – Not statistically different from manufacturers’ claim Figure 1. HM-JACKarc Linearity Table 3. HM-JACKarc Sample Stability HM-JACKarc Measured Stability of Diluted Hb and Faecal Samples Spiked with Hb Temperature - 20˚C 4˚C 20˚C Concentration (µg Hb/g faeces) All concs All concs All concs Hb in buffer STS STS STS Hb in faeces STS STS STS KEY: STS – Stable throughout study (30 days) i.e. the concentration of Hb did not fall below 50% of the initial concentration during the study. Concs – haemoglobin concentrations. Four concentrations of Hb were tested ranging from the detection limit to a strong positive FIT result.
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