A randomised controlled trial and economic evaluation of intraoperative cell salvage during caesarean section in women at risk of haemorrhage: The salvo (cell salvage in obstetrics) trial

Health Technology Assessment

Volumn 22, Issue 2, 2018, Pages 1-87

  Khan, Khalid S ^a   Moore, Philip ^b   Wilson, Matthew ^c   Hooper, Richard ^d   Allard, Shubha ^e   Wrench, Ian ^f   Roberts, Tracy ^g   McLoughlin, Carol ^g   Beresford, Lee ^d   Geoghegan, James ^b   Daniels, Jane ^h   Catling, Sue ⁱ   Clark, Vicki A ^j   Ayuk, Paul ^k   Robson, Stephen ^l   Gao Smith, Fang ^g   Hogg, Matthew ^m   Jackson, Louise ^g   Lanz, Doris ^a   Dodds, Julie ^a  

^a QUEEN MARY UNIVERSITY OF LONDON   (United Kingdom)

^b BIRMINGHAM WOMEN S HOSPITAL   (United Kingdom)

^c UNIVERSITY OF SHEFFIELD   (United Kingdom)

^d QUEEN MARY UNIVERSITY OF LONDON   (United Kingdom)

^e NHS BLOOD AND TRANSPLANT   (United Kingdom)

^f SHEFFIELD TEACHING HOSPITALS NHS FOUNDATION TRUST   (United Kingdom)

^g UNIVERSITY OF BIRMINGHAM   (United Kingdom)

^h UNIVERSITY OF NOTTINGHAM   (United Kingdom)

ⁱ SINGLETON HOSPITAL   (United Kingdom)

^j UNIVERSITY OF EDINBURGH   (United Kingdom)

^k ROYAL VICTORIA INFIRMARY   (United Kingdom)

^l NEWCASTLE UNIVERSITY   (United Kingdom)

^m ROYAL LONDON HOSPITAL   (United Kingdom)

more..

Author keywords

[No Author keywords available]

Indexed keywords

HEMOGLOBIN; RHESUS D ANTIBODY;

ADULT; ALLOIMMUNIZATION; AMNION FLUID EMBOLISM; ARTICLE; BLOOD DONOR; BLOOD TRANSFUSION; CESAREAN SECTION; CONTROLLED STUDY; COST EFFECTIVENESS ANALYSIS; DISEASE ASSOCIATION; ECONOMIC EVALUATION; ELECTIVE SURGERY; FATIGUE; FEMALE; FETOMATERNAL TRANSFUSION; HEALTH HAZARD; HEMOGLOBIN BLOOD LEVEL; HUMAN; INTRAOPERATIVE CELL SALVAGE; INTRAOPERATIVE PERIOD; LENGTH OF STAY; LONG TERM CARE; MOBILIZATION; MULTICENTER STUDY; OBSTETRIC EMERGENCY; OBSTETRIC HEMORRHAGE; OBSTETRIC PROCEDURE; OUTCOME ASSESSMENT; PRIMARY MEDICAL CARE; PROPHYLAXIS; RANDOMIZED CONTROLLED TRIAL; RHESUS INCOMPATIBILITY; RISK FACTOR; SECONDARY HEALTH CARE; SURGICAL RISK; UNITED KINGDOM; BIOMEDICAL TECHNOLOGY ASSESSMENT; BLEEDING; BLOOD SALVAGE; CLINICAL TRIAL; COST BENEFIT ANALYSIS; ECONOMICS; HEALTH CARE PLANNING; PROCEDURES; QUALITY ADJUSTED LIFE YEAR; QUALITY OF LIFE; STATISTICS AND NUMERICAL DATA;

ADULT; BLOOD TRANSFUSION; CESAREAN SECTION; COST-BENEFIT ANALYSIS; FEMALE; HEALTH RESOURCES; HEMOGLOBINS; HEMORRHAGE; HUMANS; LENGTH OF STAY; OPERATIVE BLOOD SALVAGE; QUALITY OF LIFE; QUALITY-ADJUSTED LIFE YEARS; TECHNOLOGY ASSESSMENT, BIOMEDICAL; UNITED KINGDOM;

EID: 85040786534     PISSN: 13665278     EISSN: 20464924     Source Type: Journal    
DOI: 10.3310/hta22020     Document Type: Article

References (92)

1. Centre for Maternal and Child Enquiries. Saving mothers’ lives: reviewing maternal deaths to make motherhood safer: 2006-2008. BJOG 2011;118(Suppl. 1):1-203. https://doi.org/10.1111/j.1471-0528.2010.02847.x
2. Bodelon C, Bernabe-Ortiz A, Schiff MA, Reed SD. Factors associated with peripartum hysterectomy. Obstet Gynecol 2009;114:115-23. https://doi.org/10.1097/AOG.0b013e3181a81cdd
3. Intensive Care National Audit & Research Centre. Female Admissions (Aged 16-50 Years) to Adult, General Critical Care Units in England, Wales and Northern Ireland Reported as ‘Currently Pregnant’ or ‘Recently Pregnant’. London: ICNARC; 2013.
4. Lataifeh I, Amarin Z, Zayed F, Al-Mehaisen L, Alchalabi H, Khader Y. Indications and outcome for obstetric patients’ admission to intensive care unit: a 7-year review. J Obstet Gynaecol 2010;30:378-82. https://doi.org/10.3109/01443611003646298
5. Saravanakumar K, Davies L, Lewis M, Cooper GM. High dependency care in an obstetric setting in the UK. Anaesthesia 2008;63:1081-6. https://doi.org/10.1111/j.1365-2044.2008.05581.x
6. Bateman BT, Berman MF, Riley LE, Leffert LR. The epidemiology of postpartum hemorrhage in a large, nationwide sample of deliveries. Anesth Analg 2010;110:1368-73. https://doi.org/10.1213/ANE.0b013e3181d74898
7. Holm C, Langhoff-Roos J, Petersen KB, Norgaard A, Diness BR. Severe postpartum haemorrhage and mode of delivery: a retrospective cohort study. BJOG 2012;119:596-604. http://dx.doi.org/10.1111/j.1471-0528.2011.03267.x
8. Betran AP, Torloni MR, Zhang JJ, Gülmezoglu AM, WHO Working Group on Caesarean Section. WHO Statement on Caesarean Section Rates. BJOG 2016;123:667-70. https://doi.org/10.1111/1471-0528.13526
9. Hospital Episode Statistics Analysis and Health and Social Care Information Centre. NHS Maternity Statistics - England 2013-14. 2015. URL: http://content.digital.nhs.uk/catalogue/PUB16725/nhs-mate-eng-2013-14-summ-repo-rep.pdf
10. Healthcare Improvement Scotland. Scottish Confidential Audit of Severe Maternal Morbidity: Reducing Avoidable Harm. Tenth annual report. Edinburgh: Healthcare Improvement Scotland; 2014. URL: www.healthcareimprovementscotland.org/our_work/reproductive,_material_child/programme_resources/scasmm.aspx (accessed 18 September 2017).
11. Tinegate H, Pendry K, Murphy M, Babra P, Grant-Casey J, Hopkinson C, et al. Where do all the red blood cells (RBCs) go? Results of a survey of RBC use in England and North Wales in 2014. Transfusion 2016;56:139-45. https://doi.org/10.1111/trf.13342
12. National Institute for Health and Care Excellence. Costing Statement: Blood Transfusion. Implementing the NICE Guideline on Blood Transfusion (NG24). London: NICE; 2015.
13. NHS Blood and Transplant. Saving and Improving Lives. Strategic Plan 2015-20. NHS Blood and Transplant; 2015. URL: https://nhsbtdbe.blob.core.windows.net/umbraco-assets-corp/1593/strategic_plan_2015_20.pdf (accessed 18 September 2017).
14. Shander A, Isbister J, Gombotz H. Patient blood management: the global view. Transfusion 2016;56(Suppl. 1):94-102. https://doi.org/10.1111/trf.13529
15. Mehra T, Seifert B, Bravo-Reiter S, Wanner G, Dutkowski P, Holubec T, et al. Implementation of a patient blood management monitoring and feedback program significantly reduces transfusions and costs. Transfusion 2015;55:2807-15. http://dx.doi.org/10.1111/trf.13260
16. Catling S. Intraoperative cell salvage in obstetrics. Clinical Risk 2008;14:14-17. http://dx.doi.org/10.1258/cr.2007.070009
17. Bolton-Maggs P, Poles D, Watt A, Thomas D. The Annual SHOT Report 2013. Manchester: SHOT 2014. URL: www.shotuk.org/wp-content/uploads/Annual-SHOT-Report-2013-Bookmarked.pdf (accessed 18 September 2017).
18. Bolton-Maggs P, Poles D, et al., on behalf of the Serious Hazards of Transfusion (SHOT) Steering Group. The 2015 Annual SHOT Report 2016. URL: www.shotuk.org/wp-content/uploads/SHOT-2015-Annual-Report-Web-Edition-Final-bookmarked.pdf (accessed 18 September 2017).
19. Shander A, Knight K, Thurer R, Adamson J, Spence R. Prevalence and outcomes of anemia in surgery: a systematic review of the literature. Am J Med 2004;116(Suppl. 7A):58-69. https://doi.org/10.1016/j.amjmed.2003.12.013
20. James AH, Patel ST, Watson W, Zaidi QR, Mangione A, Goss TF. An assessment of medical resource utilization and hospitalization cost associated with a diagnosis of anemia in women with obstetrical bleeding in the United States. J Womens Health (Larchmt) 2008;17:1279-84. http://dx.doi.org/10.1089/jwh.2007.0605
21. Carless PA, Henry DA, Moxey AJ, O’Connell D, Brown T, Fergusson DA. Cell salvage for minimising perioperative allogeneic blood transfusion. Cochrane Database Syst Rev 2010;4:CD001888. http://dx.doi.org/10.1002/14651858.CD001888.pub3
22. Davies L, Brown TJ, Haynes S, Payne K, Elliott RA, McCollum C. Cost-effectiveness of cell salvage and alternative methods of minimising perioperative allogeneic blood transfusion: a systematic review and economic model. Health Technol Assess 2006;10(44). https://doi.org/10.3310/hta10440
23. Sreelakshmi TR, Eldridge J. Acute hypotension associated with leucocyte depletion filters during cell salvaged blood transfusion. Anaesthesia 2010;65:742-4. http://dx.doi.org/10.1111/j.1365-2044. 2009.06190.x
24. Kessack LK, Hawkins N. Severe hypotension related to cell salvaged blood transfusion in obstetrics. Anaesthesia 2010;65:745-8. https://doi.org/10.1111/j.1365-2044.2010.06301.x
25. Waldron S. Hypotension associated with leucocyte depletion filters following cell salvage in obstetrics. Anaesthesia 2011;66:133-4. https://doi.org/10.1111/j.1365-2044.2010.06588.x
26. Zoon KC, Jacobson ED, Woodcock J. Hypotension and bedside leukocyte reduction filters. Int J Trauma Nurs 1999;5:121-2. https://doi.org/10.1016/S1075-4210(99)90002-0
27. Sullivan I, Faulds J, Ralph C. Contamination of salvaged maternal blood by amniotic fluid and fetal red cells during elective Caesarean section. Br J Anaesth 2008;101:225-9. https://doi.org/10.1093/bja/aen135
28. Waters JH, Biscotti C, Potter PS, Phillipson E. Amniotic fluid removal during cell salvage in the cesarean section patient. Anesthesiology 2000;92:1531-6. https://doi.org/10.1097/00000542-200006000-00008
29. Mulder JI. Amniotic fluid embolism: an overview and case report. Am J Obstet Gynecol 1985;152:430-5. https://doi.org/10.1016/S0002-9378(85)80153-8
30. Clark SL, Pavlova Z, Greenspoon J, Horenstein J, Phelan JP. Squamous cells in the maternal pulmonary circulation. Am J Obstet Gynecol 1986;154:104-6. https://doi.org/10.1016/0002-9378(86)90402-3
31. Lee W, Ginsburg KA, Cotton DB, Kaufman RH. Squamous and trophoblastic cells in the maternal pulmonary circulation identified by invasive hemodynamic monitoring during the peripartum period. Am J Obstet Gynecol 1986;155:999-1001. https://doi.org/10.1016/0002-9378(86)90334-0
32. Kuhlman K, Hidvegi D, Tamura RK, Depp R. Is amniotic fluid material in the central circulation of peripartum patients pathologic? Am J Perinatol 1985;2:295-9. https://doi.org/10.1055/s-2007-999974
33. White J, Qureshi H, Massey E, Needs M, Byrne G, Daniels G, Allard S, British Committee for Standards in Haematology. Guideline for blood grouping and red cell antibody testing in pregnancy. Transfus Med 2016;26:246-63. https://doi.org/10.1111/tme.12299
34. Qureshi H, Massey E, Kirwan D, Davies T, Robson S, White J, et al. BCSH guideline for the use of anti-D immunoglobulin for the prevention of haemolytic disease of the fetus and newborn. Transfus Med 2014;24:8-20. https://doi.org/10.1111/tme.12091
35. Royal College of Obstetricians and Gynaecologists. The Management of Women with Red Cell Antibodies during Pregnancy. RCOG Green-top Guideline No. 65. London: Royal College of Obstetricians and Gynaecologists; 2014.
36. Dhariwal SK, Khan KS, Allard S, Wilson M, Moore P, SALVO study group. Does current evidence support the use of intraoperative cell salvage in reducing the need for blood transfusion in caesarean section? Curr Opin Obstet Gynecol 2014;26:425-30. https://doi.org/10.1097/GCO.0000000000000116
37. Ralph CJ, Sullivan I, Faulds J. Intraoperative cell salvaged blood as part of a blood conservation strategy in Caesarean section: is fetal red cell contamination important? Br J Anaesth 2011;107:404-8. https://doi.org/10.1093/bja/aer168
38. National Institute for Health and Care Excellence. Intraoperative Blood Cell Salvage in Obstetrics. Guideline IPG144. London: NICE; 2005.
39. Association of Anaesthetists of Great Britain and Ireland. Blood Transfusion and the Anaesthetist: Intra-operative Cell Salvage. London: Association of Anaesthetists of Great Britain and Ireland; 2009.
40. Royal College of Obstetricians and Gynaecologists. Blood Transfusion in Obstetrics (Green-top Guideline No. 47). London: Royal College of Obstetricians and Gynaecologists; 2007.
41. Teig M, Harkness M, Catling S, Clark V. Survey of Cell-salvage Use in Obstetrics in the UK. Paper presented at Annual Meeting of the Obstetric Anaesthetists Association, Sheffield, UK, 2007.
42. Evans H, Lewis E. UK survey of the availability of cell salvage and interventional radiological services for the management of obstetric haemorrhage. Int J Obstet Anesth 2013;22:355-6. http://dx.doi.org/10.1016/j.ijoa.2013.05.006
43. Geoghegan J, Daniels JP, Moore PA, Thompson PJ, Khan KS, Gülmezoglu AM. Cell salvage at caesarean section: the need for an evidence-based approach. BJOG 2009;116:743-7. https://doi.org/10.1111/j.1471-0528.2009.02129.x
44. Rainaldi MP, Tazzari PL, Scagliarini G, Borghi B, Conte R. Blood salvage during caesarean section. Br J Anaesth 1998;80:195-8. https://doi.org/10.1093/bja/80.2.195
45. Rebarber A, Lonser R, Jackson S, Copel JA, Sipes S. The safety of intraoperative autologous blood collection and autotransfusion during cesarean section. Am J Obstet Gynecol 1998;179:715-20. https://doi.org/10.1016/S0002-9378(98)70070-5
46. Catling SJ, Freites O, Krishnan S, Gibbs R. Clinical experience with cell salvage in obstetrics: 4 cases from one UK centre. Int J Obstet Anesth 2002;11:128-34. https://doi.org/10.1054/ijoa.2001.0914
47. Keeling MM, Gray LA, Brink MA, Hillerich VK, Bland KI. Intraoperative autotransfusion. Experience in 725 consecutive cases. Ann Surg 1983;197:536-41. https://doi.org/10.1097/00000658-198305000-00006
48. Jackson SH, Lonser RE. Safety and effectiveness of intracesarean blood salvage. Transfusion 1993;33:181. https://doi.org/10.1046/j.1537-2995.1993.33293158054.x
49. Potter PS, Waters JH, Burger GA, Mraovic´ B. Application of cell-salvage during cesarean section. Anesthesiology 1999;90:619-21. https://doi.org/10.1097/00000542-199902000-00038
50. Rees SG, Boheimer NO. Autologous blood transfusion. Br J Anaesth 1998;80:563. https://doi.org/10.1093/bja/80.4.563
51. Waters JH, Lukauskiene E, Anderson ME. Intraoperative blood salvage during cesarean delivery in a patient with beta thalassemia intermedia. Anesth Analg 2003;97:1808-9. https://doi.org/10.1213/01.ANE.0000087046.91072.E8
52. Grimes DA. A simplified device for intraoperative autotransfusion. Obstet Gynecol 1988;72:947-50. https://doi.org/10.1097/00006250-198812000-00030
53. Katz AR, Walker WA, Ross PJ, Held B. Autologous transfusion in obstetrics and gynecology. Int J Gynaecol Obstet 1978;16:345-7. https://doi.org/10.1002/j.1879-3479.1979.tb00461.x
54. Zichella L, Gramolini R. Autotransfusion during cesarean section. AmJ Obstet Gynecol 1990;162:295. https://doi.org/10.1016/0002-9378(90)90880-G
55. Geoghegan J, Middleton L, Moore P, Subseson G, Khan K, Daniels J. Routine cell salvage during elective caesarean section: a pilot randomised trial. Int J Obstet Anesth 2015;24:86-7. https://doi.org/10.1016/j.ijoa.2014.08.003
56. Torloni MR, Betran AP, Souza JP, Widmer M, Allen T, Gulmezoglu M, Merialdi M. Classifications for cesarean section: a systematic review. PLOS ONE 2011;6:e14566. https://doi.org/10.1371/journal.pone.0014566
57. Royal College of Obstetricians and Gynaecologists. The Royal College of Anaesthetists. Classification of Urgency of Caesarean Section - A Continuum of Risk. Good Practice Guideline No. 11. London: Royal College of Obstetricians and Gynaecologists; 2010.
58. Lucas DN, Yentis SM, Kinsella SM, Holdcroft A, May AE, Wee M, Robinson PN. Urgency of caesarean section: a new classification. J R Soc Med 2000;93:346-50. https://doi.org/10.1177/014107680009300703
59. National Institute for Health and Care Excellence. Intrapartum Care: Care of Healthy Women and their Babies During Childbirth. Clinical Guideline CG55. London: NICE; 2007.
60. National Institute for Health and Care Excellence. Intrapartum Care for Healthy Women and Babies. Clinical Guideline CG190. London: NICE; 2014.
61. Haynes SL, Bennett JR, Torella F, McCollum CN. Does washing swabs increase the efficiency of red cell recovery by cell salvage in aortic surgery? Vox Sang 2005;88:244-8. https://doi.org/10.1111/j.1423-0410.2005.00631.x
62. Smets EM, Garssen B, Bonke B, De Haes JC. The Multidimensional Fatigue Inventory (MFI) psychometric qualities of an instrument to assess fatigue. J Psychosom Res 1995;39:315-25. https://doi.org/10.1016/0022-3999(94)00125-O
63. Working Party of the British Committee for Standards in Haematology. Transfusion Taskforce. Guidelines for the Estimation of Fetomaternal Haemorrhage. London: British Society for Haematology; 2009.
64. NHS England Patient Safety Domain. Serious Incident Framework. Supporting Learning to Prevent Recurrence. London: NHS England; 2015.
65. Great Britain. Data Protection Act. London: The Stationery Office; 1998.
66. Department of Health. The Caldicott Committee. Report on the Review of Patient-Identifiable Information. London: Department of Health; 1997.
67. Department of Health. Research Governance Framework for Health and Social Care, Second Edition. London: The Stationery Office; 2005.
68. Fong J, Gurewitsch ED, Kang HJ, Kump L, Mack PF. An analysis of transfusion practice and the role of intraoperative red blood cell salvage during cesarean delivery. Anesth Analg 2007;104:666-72. https://doi.org/10.1213/01.ane.0000253232.45403.e5
69. White IR, Thompson SG. Adjusting for partially missing baseline measurements in randomized trials. Stat Med 2005;24:993-1007. https://doi.org/10.1002/sim.1981
70. White IR, Horton NJ, Carpenter J, Pocock SJ. Strategy for intention to treat analysis in randomised trials with missing outcome data. BMJ 2011;342:d40. https://doi.org/10.1136/bmj.d40
71. Royal College of Obstetricians and Gynaecologists. Prevention and Management of Postpartum Haemorrhage (Green-top Guideline No. 52). London: Royal College of Obstetricians and Gynaecologists; 2009.
72. Khan KS, Moore PAS, Wilson MJ, Hooper R, Allard S, Wrench I, et al. Cell salvage and donor blood transfusion during cesarean section: a pragmatic, multicentre randomised controlled trial (SALVO). PLOS Med 2017;14:e1002471. https://doi.org/10.1371/journal.pmed.1002471
73. Briggs AH, Claxton K, Sculpher MJ. Decision Modelling for Health Economic Evaluation. Oxford: Oxford University Press; 2006.
74. NHS Supply Chain. NHS Supply Chain Catalogue 2015. URL: https://my.supplychain.nhs.uk/Catalogue (accessed August 2016).
75. UK Cell Salvage Action Group. ICS Technical Factsheet 1: Swab Washing. 2015. URL: http://www.transfusionguidelines.org/transfusion-practice/uk-cell-salvage-action-group/technical-factsheets-andfrequently-asked-questions-faq (accessed 18 September 2017).
76. Joint Formulary Committee. British National Formulary (online). London: BMJ Group and Pharmaceutical Press. URL: www.medicinescomplete.com (accessed August 2016).
77. Curtis L. Unit Costs of Health and Social Care 2015. Canterbury: PSSRU, University of Kent; 2015.
78. NHS Blood and Transplant. Blood and Components Price List 2016/2017. 2016. URL: http://hospital.blood.co.uk/media/28230/component-price-list-2016-2017.pdf (accessed 18 September 2017).
79. Department of Health. NHS Reference Costs 2014/2015. 2015. URL: https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/477919/2014-15_Reference:costs_publication.pdf (accessed 18 September 2017).
80. NHS National Tariff Payment System. 2016/17 National Prices. 2016. URL: www.gov.uk/government/publications/national-tariff-payment-system-2014-to-2015 (accessed August 2016).
81. Tinegate H, Birchall J, Gray A, Haggas R, Massey E, Norfolk D, et al. Guideline on the investigation and management of acute transfusion reactions. Prepared by the BCSH Blood Transfusion Task Force. Br J Haematol 2012;159:143-53. https://doi.org/10.1111/bjh.12017
82. National Institute for Health and Care Excellence. Guide to the Methods of Technology Appraisal. London: NICE; 2013.
83. Gupta SK. Intention-to-treat concept: a review. Perspect Clin Res 2011;2:109-12. http://dx.doi.org/10.4103/2229-3485.83221
84. Briggs AH. A Bayesian approach to stochastic cost-effectiveness analysis. Health Econ 1999;8:257-61. https://doi.org/10.1002/(SICI)1099-1050(199905)8:3<257::AID-HEC427>3.0.CO;2-E
85. Briggs AH, Gray AM. Handling uncertainty when performing economic evaluation of healthcare interventions. Health Technol Assess 1999;3:1-134.
86. Alkema L, Chou D, Hogan D, Zhang S, Moller A-B, Gemmill A, et al. Global, regional, and national levels and trends in maternal mortality between 1990 and 2015, with scenario-based projections to 2030: a systematic analysis by the UN Maternal Mortality Estimation Inter-Agency Group. Lancet 387:462-74. http://dx.doi.org/10.1016/S0140-6736(15)00838-7
87. Say L, Chou D, Gemmill A, Tunçalp Ö, Moller AB, Daniels J, et al. Global causes of maternal death: a WHO systematic analysis. Lancet Glob Health 2014;2:e323-33. https://doi.org/10.1016/S2214-109X(14)70227-X
88. Jardine JE, Law P, Hogg M, Murphy D, Khan KS, C-SAFETY. Haemorrhage at caesarean section: a framework for prevention and research. Curr Opin Obstet Gynecol 2016;28:492-8. https://doi.org/10.1097/GCO.0000000000000328
89. Royal College of Obstetricians and Gynaecologists. Obtaining Valid Consent to Participate in Perinatal Research Where Consent is Time Critical. Clinical Governance Advice No. 6a. London: Royal College of Obstetricians and Gynaecologists; 2016.
90. George RT, Butcher M, Yentis SM. Pregnant women’s views on informed consent for research in labour. Int J Obstet Anesth 2014;23:233-7. https://doi.org/10.1016/j.ijoa.2014.03.004
91. Wood J, Freemantle N, King M, Nazareth I. Trap of trends to statistical significance: likelihood of near significant P value becoming more significant with extra data. BMJ 2014;348:g2215. https://doi.org/10.1136/bmj.g2215
92. SHOT. SHOT Annual Reports and Summaries. 2017. URL: www.shotuk.org/shot-reports (accessed 6 September 2017).