Appendix 1: Detailed break-down of test costs according to micro-costing
- Cell culture cytotoxin neutralization assay (CCNA)
Resource / List price (£) / Pack size / Unit cost (£) / Resource use per test / Cost per test (£) / Comment / Source
Consumables and reagents:
Universal container (Sterilin) / 57.99 / 400 / 0.14 / 1.00 / 0.14 / (September 2011)
Phosphate buffered saline / 81.00 / 1000 ml / 0.08 / 10.00 ml / 0.81 / made onsite, ready-made price used / (September 2011)
Micro plate (confluent layer of Vero cells in maintenance medium containing HEPES) incl. lid / 58.00 / 50 / 1.16 / 0.02 / 0.02 / 96 wells, 2 per test needed + positive and negative controls / (September 2011)
20 µl Clostridium sordelli antitoxin / 60.00 / 500000 µl / 0.0001 / 20.00 µl / 0.0024 / 5 ml bottle, diluted 1:100, 20 µl/test / Purchasing Singelton Hospital, Swansea, UK
Pipette or swab / 4.40 / 500 / 0.01 / 1.00 / 0.01 / Purchasing Singleton Hospital, Swansea, UK
Pipette tip (20 µl) / 31.79 / 2000 / 0.02 / 2.00 / 0.03 / (September 2011)
Tissue culture flasks (75 cm2) / 211.41 / 100 / 2.11 / 0.01 / 0.01 / one flask for 4 plates (152 samples), 2 wells per sample / (September 2011)
Other reagents / 0.50 / 1 / 0.50 / 1.00 / 0.50 / includes continuous line of cells and its maintenance and positive control / Head of laboratory and purchasing Singleton Hospital, Swansea, UK
Foetal bovine serum / 30.00 / 500 / 0.06 / 0.30 / 0.02 / one flask (30 ml) makes 4 plates (152 samples) / Purchasing Singleton Hospital, Swansea, UK
Tissue culture media (HEPES) / 17.40 / 1000 / 0.02 / 0.30 / 0.01 / one flask (30 ml) makes 4 plates (152 samples) / (September 2011)
Gloves / 4.87 / 100 / 0.05 / 0.25 / 0.01 / glove change every 4 samples assumed / Purchasing Singleton Hospital, Swansea, UK
Total (consumables and reagents): / £1.57
Material waste / 0.08 (5% of total consumable cost) / 0.0023 / 0.0002 / on average 34 samples received per day, materials for 38 prepared, 5% wasted / Head of Virology, laboratory staff
Capital and overheads:
Overheads / 2.00 / Estimate (includes space needed, cell culture, lighting, electricity, cleaning, maintenance) / Estimate
Centrifuge (Sorval Legend RT) / 6804.00 / 50000 / 0.14 / 1.00 / 0.14 / 5 year lifespan assumed, 10,000 samples a year, assumption made that only used for CCNA / Purchasing Singleton Hospital, Swansea, UK
Hospital statistics
Maintenance contract Centrifuge / 210.00 / 10000 / 0.02 / 1.00 / 0.02 / £ 210 per year / Purchasing Singleton Hospital, Swansea, UK
Class 1 microbiological safety cabinet (Leec) / 10000.00 / 50000 / 0.20 / 1.00 / 0.20 / 5 year lifespan assumed, 10,000 samples a year, assumption made that only used for CCNA / Purchasing Singleton Hospital, Swansea, UK
Hospital statistics
Maintenance contract safety cabinet / 72.00 / 10000 / 0.01 / 1.00 / 0.01 / £ 72 per year / Purchasing Singleton Hospital, Swansea, UK
Vortex (Whirlimixer) / 500.00 / 50000 / 0.01 / 1.00 / 0.01 / 5 year lifespan assumed, 10,000 samples a year, assumption made that only used for CCNA / Purchasing Singleton Hospital, Swansea, UK
Hospital statistics
Incubator (Leec Research CO2) / 5000.00 / 50000 / 0.10 / 1.00 / 0.10 / 5 year lifespan assumed, 10,000 samples a year, assumption made that only used for CCNA / Purchasing Singleton Hospital, Swansea, UK
Hospital statistics
Maintenance contract microscope / 54.00 / 10000 / 0.01 / 1.00 / 0.01 / £ 54 per year / Purchasing Singleton Hospital, Swansea, UK
Microscope / 5000.00 / 50000 / 0.10 / 1.00 / 0.10 / 5 year lifespan assumed, 10,000 samples a year, assumption made that only used for CCNA / Purchasing Singleton Hospital, Swansea, UK
Hospital statistics
Total (overhead and capital): / £2.58
Staff costs:
Sample labelling / 7.69/hour / 60 mins / 0.13/min / 2.00 mins / 0.26 / Band 2 (£ 15,194) / Laboratory staff and personnel department
Sample preparation / 7.69/hour / 60 mins / 0.13/min / 4.50 mins / 0.58 / Band 2 (£ 15,194), 45 mins for 10 samples / Laboratory staff and personnel department
Tidying up / 7.69/hour / 60 mins / 0.13/min / 0.50 mins / 0.06 / Band 2 (£ 15,194), 5 mins for 10 samples / Laboratory staff and personnel department
Cataloguing / 7.69/hour / 60 mins / 0.13/min / 0.50 mins / 0.06 / Band 2 (£ 15,194), 5 mins for 10 samples / Laboratory staff and personnel department
Sample reading (18 hours) / 14.91/hour / 60 mins / 0.25/min / 5.00 mins / 1.24 / Band 6 (£ 29,464), 30 mins for 6 samples / Laboratory staff and personnel department
Sample reading (48 hours) / 14.91/hour / 60 mins / 0.25/min / 5.00 mins / 1.24 / Band 6 (£ 29,464), 30 mins for 6 samples / Laboratory staff and personnel department
Reporting of results / 14.91/hour / 60 mins / 0.25/min / 2.00 mins / 0.50 / Band 6 (£ 29,464), 30 mins for 6 samples / Laboratory staff and personnel department
Staff training (preparation, trainee time) / 7.69/hour / 60 mins / 0.13/min / 0.19 / 0.02 / Band 2 (£ 15,194), assumed 4 days a year = 32 hours = 1920 minutes per 10,000 samples / Laboratory staff and personnel department
Staff training (preparation, trainer time) / 14.91/hour / 60 mins / 0.25/min / 0.19 / 0.05 / Band 6 (£ 29,464), assumed 4 days a year = 32 hours = 1920 minutes per 10,000samples / Laboratory staff and personnel department
Staff training (reading, trainee time) / 14.91/hour / 60 mins / 0.25/min / 0.19 / 0.05 / Band 6 (£ 29,464), assumed 4 days a year = 32 hours = 1920 minutes per 10,000samples / Laboratory staff and personnel department
Staff training (reading, trainer time) / 14.91/hour / 60 mins / 0.25/min / 0.19 / 0.05 / Band 6 (£ 29,464), assumed 4 days a year = 32 hours = 1920 minutes per 10,000samples / Laboratory staff and personnel department
Total (staff): / 20.27 mins / £ 4.11
Repeat samples / 9.00 (approx. test cost) / 0.06 / 0.51 / 59/1034 samples positive PCR but negative CCNA; would be sent again = 5.7 % of samples / Clinical study data [17]
Total cost/test CCNA: / £8.78
- Xpert C. difficile rtPCR
Resource / List price (£) / Pack size / Unit cost (£) / Resource use/test / Cost per test (£) / Comment / Source
Consumables and reagents:
PCR kit (incl. cartridge and reagents) / 333.50 / 10 / 33.35 / 1.00 / 33.35 / Cepheid (no discount applied)
Sterile swab / 14.91 / 100 / 0.15 / 1.00 / 0.15 / (September 2011)
Gloves / 4.87 / 100 / 0.05 / 0.13 / 0.01 / Glove change every 8 samples assumed / Purchasing Singleton Hospital, Swansea, UK
Total (consumables and reagents): / £33.51
Material waste / 33.51 / 0.03 / 1.08 / one repeat sample per 31 samples / Clinical trial data (33 repeats in 1051 samples) [17]
Capital and overheads:
Overheads / 0.02 / adjusted according to space taken up in comparison to CCNA / Estimate
Cepheid GeneXpert PCR (16-8) / 63600.00 / 100000 / 0.64 / 1.00 / 0.64 / 10 year life span = 124000 samples (mean 10,000 per year) / Cepheid and ABMUHB statistics (assumption as machine only on market since 2006
Maintenance contract (16-8) / 18221.00 / 50000 / 0.36 / 1.00 / 0.36 / 5 year warranty = 62000 samples (mean 10,000 per year) / Cepheid and ABMUHB statistics
Total (overhead and capital): / £1.02
Staff costs:
Sample labelling / 7.69/hour / 60 mins / 0.13/min / 1.00 min / 0.13 / Band 2 (£ 15,194), 1 mins per sample / Laboratory staff and personnel department
Sample preparation and test start / 7.69/hour / 60 mins / 0.13/min / 1.50 mims / 0.19 / Band 2 (£ 15,194), 1.5 mins per sample / Laboratory staff and personnel department
Tidying up and entry on Masterlab / 7.69/hour / 60 mins / 0.13/min / 0.60 mins / 0.08 / Band 2 (£ 15,194), 0.6 mins per sample / Laboratory staff and personnel department
Staff training (preparation, trainee time) / 7.69/hour / 60 mins / 0.13/min / 0.01 mins / 0.001 / Band 2 (£ 15,194), assumed 0.2 days a year = 1.6 hours = 96.0 minutes per 10,000 samples = 0.0096 mins per sample / Laboratory staff and personnel department
Staff training (preparation, trainer time) / 14.91/hour / 60 mins / 0.25/min / 0.01 mins / 0.002 / Band 6 (£ 29,464), assumed 0.2 days a year = 1.6 hours = 96.0 minutes per 10,000 samples = 0.0096 mins per sample / Laboratory staff and personnel department
Results check / 14.91/hour / 60 mins / 0.25/min / 0.20 mins / 0.05 / Band 6 (£ 29,464) / Laboratory staff and personnel department
Reporting of results / 14.91/hour / 60 mins / 0.25/min / 0.50 mins / 0.12 / Band 6 (£ 29,464) / Laboratory staff and personnel department
Total (staff): / 3.82 mins / £ 0.57
Total cost/test PCR: / £36.18
Appendix 2: Calculation of potential cost savings of rtPCR compared to routine CCNA
Parameter / Value / Comment / Calculation / Source(1) Samples/year by routine CCNA / 10,769 / Number of samples tested in ABMUHB 2011 / n/a / ABMUHB laboratory statistics
(2) Positive patients/year (CCNA) / 289 / Number of positives (all ages) in ABMUHB 2011 / n/a / Mandatory Surveillance Report, Public Health Wales for 20111
(2a) Percentage of positive samples / 0.0268 / Percentage of positive samples in ABMUHB in 2011 / Positives(2)/Samples(1)
(3) Negative samples/year / 10,480 / Number of negative samples per year / Samples(1) – positives(2)
(3a) Negative patients/year / 5,240 / Assumption made that negative CCNA tests will be repeated once per patient2 / Hospital statistics suggest high rate of repeat samples for CCNA
(4) Cost testing CCNA (all samples); £ / 94,502.67 / Assumption made that initially negative CCNA tests need to be repeated once per patient2 / Cost/test CCNA [£8.78]* samples(1) / ABMUHB laboratory statistics and micro-costing
(5) Cost testing PCR (all samples); £ / 200,040.21 / Only half of negative samples tested i.e. every patient tested once2 / (Cost/test PCR [£36.18]* positives(1))+(Cost/test PCR [£36.18]* negatives(3a)) / ABMUHB laboratory statistics and micro-costing
(6) Incremental cost PCR; £ / 105,537.54 / Cost PCR(5) - cost CCNA(4)
(7) Positives earlier discharge; days / 4.88 / Mean study result PCR-CCNA / Mean difference according to study result
(8) Negatives earlier discharge; days / 7.03 / Mean study result PCR-CCNA / Mean difference according to study result
(9) Bed days saved positives / 1,410.32 / Mean bed days saved in 2011 for all positive patients by using PCR instead of CCNA / Positives earlier discharge(7)*positives(2)
(10) Bed days saved negatives / 36,837.20 / Mean bed days saved in 2011 for all negative patients by using PCR instead of CCNA; assumed all patients tested twice with CCNA2 / Negatives earlier discharge(8)*negative patients(3a)
(11) Cost per bed day; £ / 334.17 / Weighted for speciality and activity / NHS reference costs 20113
(12) Cost savings/positive; £ / 1,630.75 / Potential cost saving per positive patient by using PCR instead of CCNA / Positives earlier discharge(7)*cost per bed day(11)
(13) Cost savings/negative; £ / 2,349.22 / Potential cost saving per negative patient by using PCR instead of CCNA / Negatives earlier discharge(8)*cost per bed day(11)
(14) Savings all positives; £ / 470,649.34 / Total potential cost savings for all positive samples in ABMUHB in 2011 if PCR is used instead of CCNA / Bed days saved positive(9)*cost per bed day(11)
(15) Savings all negatives; £ / 12,310,346.16 / Total potential cost savings for all negative samples in ABMUHB in 2011 if PCR is used instead of CCNA / Bed days saved negative(10)*cost per bed day(11)
(16) Total savings; £ / 12,780,995.50 / Savings positive(14) +savings negative(15)
(17) Total net savings; £ / 12,675,457.96 / Total potential net savings of PCR compared to CCNA in ABMUHB in 2011 / Total savings(16) - incremental cost PCR(6)
(18) Cost savings per patient; £ / 2292.62 / Potential cost savings of PCR compared to CCNA in ABMUHB in 2011 per patient / Net savings(17)/
(positives(2) + negative patients(3a))
1 Welsh Healthcare Associated Infection Programme. Clostridium difficile. Mandatory Surveillance Report. Abertawe Bro Margannwg University Health Board. Public Health Wales. 2012: page 8 [19].
2For the calculations it was assumed that negative CCNA samples would be repeated twice per patient while negative PCR samples would only be done once. This assumption is based on a high rate of repeat samples for CCNA testing according to ABMUHB laboratory statistics and recent literature suggesting a significant drop in repeat samples after introduction of PCR [37]
3Department of Health. NHS reference costs 2010-2011. Department of Health 2012, United Kingdom [18].