| Literature DB >> 27231544 |
Shanshan Zhang1, Peter M Sammon2, Isobel King3, Ana Lucia Andrade4, Cristiana M Toscano4, Sheila N Araujo5, Anushua Sinha6, Shabir A Madhi7, Gulam Khandaker8, Jiehui Kevin Yin8, Robert Booy8, Tanvir M Huda9, Qazi S Rahman10, Shams El Arifeen10, Angela Gentile11, Norberto Giglio11, Mejbah U Bhuiyan12, Katharine Sturm-Ramirez13, Bradford D Gessner14, Mardiati Nadjib15, Phyllis J Carosone-Link16, Eric Af Simões17, Jason A Child18, Imran Ahmed19, Zulfiqar A Bhutta19, Sajid B Soofi20, Rumana J Khan21, Harry Campbell2, Harish Nair22.
Abstract
BACKGROUND: Childhood pneumonia is a major cause of childhood illness and the second leading cause of child death globally. Understanding the costs associated with the management of childhood pneumonia is essential for resource allocation and priority setting for child health.Entities:
Mesh:
Year: 2016 PMID: 27231544 PMCID: PMC4871066 DOI: 10.7189/jogh.06.010408
Source DB: PubMed Journal: J Glob Health ISSN: 2047-2978 Impact factor: 4.413
Figure 1Formula for the mean total cost of treatment per episode.
Figure 2PRISMA flow diagram for severe pneumonia cost systematic review.
Cost per episode for childhood pneumonia management in high–income countries
| Severity | WHO region | Country, publication year | Perspective | Sample size | Cost per episode (2013 US$) | Cost component, % of total cost per episode | |||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| AMR | US, 2012* | Societal | 940 | 334.6 | |||||||
| Chile, 2007 [ | Healthcare | 366 | 272.7 | ||||||||
| Uruguay, 2007 [ | Healthcare | 366 | 55.8 | ||||||||
| AMR | Chile, 2007 [ | Healthcare | 366 | 4316.7 | 100 | ||||||
| Uruguay, 2007 [ | Healthcare | 366 | 1421.6 | 100 | |||||||
| US, 2012* | Societal | 940 | 15 029.2 | ||||||||
| EUR | North Ireland, 1999 [ | NA | 45 | 5733.8, 2716.8 | 100 | ||||||
| WPR | Australia, 2011* | Societal | NA | 6,259.1 | 93.1 | 6.9 | |||||
| WPR | Australia, 2008 [ | Societal | 528 | 2813.1 | 254.9 | 100 | |||||
| Australia, 2008 [ | Healthcare | 1348 | 2307.8 | 100 | |||||||
| EUR | Germany, 2005 [ | Societal | 402 | 3158.6 | 251.1 | 41.5 | 19.5 | 38.5 | |||
| Spain, 2013 [ | Healthcare | 101 | 5447.3 | 100 | |||||||
| AMR | US, 2012* | Societal | 940 | 120 576.2 | |||||||
| AMR | Spain, 2013 [ | Healthcare | 101 | 9151.3 | |||||||
NA – Information not available, EUR – Europe Region, AMR – The Americas Region, WPR – Western Pacific Region, CI – confidence interval, IMCI – Integrated Management of Childhood Illness
*Unpublished data.
Cost per episode for childhood pneumonia management in low– and middle–income countries
| Severity | WHO region | Country, publication year | Perspective | Sample size | Cost per episode (2013 US$) | Cost component, % of total cost per episode | |||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| SEAR | Viet Nam, 2010 [ | Healthcare | 788 | 28.6 | |||||||
| Pakistan, 2008 [ | Healthcare | 141 | 29.4 | ||||||||
| Pakistan, 2006 [ | Societal | 502 | 94.1–17.8 | ||||||||
| Bangladesh, 2012* | Societal | 340 | 5.7 | ||||||||
| AFR | Guinea, 1998 [ | NA | 73 650 | 3.2 | |||||||
| South Africa, 2012 [ | Societal/health care | 745 | 263.1 | ||||||||
| AMR | Brazil, 2007 [ | Healthcare | 366 | 93.0 | |||||||
| SEAR | Pakistan, 2010* | Healthcare | NA | 8.7 | 100 | ||||||
| Pakistan, 2012 [ | Household | 423 | 7.9 | 1.5 | 89.1 | 1.3 | 9.6 | ||||
| Bangladesh, 2012* | Societal | 340 | 5.7 | ||||||||
| Bangladesh, 2010 [ | Societal | 360 | 193.6 | 124.0 | Y | Y | |||||
| Viet Nam, 2010 [ | Healthcare | 788 | 39.5 | Y | Y | Y | |||||
| Pakistan, 2008 [ | Healthcare | 141 | 186.0 | 64.1 | 35.9 | ||||||
| Pakistan, 2003 [ | NA | 126 | 20.3 | 100 | |||||||
| Bangladesh, 2005* | Household | 114 | 80.6† | 62.6# | 70.9† | 29.1† | |||||
| Bangladesh, 2010 [ | Household | 90 | 124.2 | 67.6 | 32.4 | ||||||
| Indonesia, 2001* | Societal | NA | 135.2 | 75 | 25 | ||||||
| AFR | Guinea, 1998 [ | NA | 73650 | 110.6 | 69 | 30 | |||||
| South Africa, 2001* | Societal | 509 | 480.9§ | 110.0 | |||||||
| AMR | Brazil, 2007 [ | Healthcare | 366 | 461.0 | 100 | ||||||
| Brazil, 2011* | Societal | 79 | 1474.1†,‡ | 594.5# | 94† | 1† | 5† | ||||
| Colombia, 2013 [ | Healthcare | 1545 | 517.6 | 100 | |||||||
| Argentina, 2012* | Societal | NA | 1648.0 | 100 | |||||||
| SEAR | Viet Nam, 2001 [ | Household | 94 | 2.7 | 56–88 | Y | |||||
| Pakistan, 2006 [ | Societal | 502 | 310.8 | 127.6 | 45.3 | 55 | |||||
| India, 2009 [ | Healthcare/household | 56 | 145.7 | 44.7 | 45.7 | 5.3 | 47.4 | ||||
| India, 2002 [ | Societal | 52 | 23.9 | 100 | |||||||
| AFR | Zambia, 2009 [ | Healthcare | 9146 | 249.7 | 55.7 | 100 | |||||
| Kenya, 2009 [ | Societal | 205 | 236.8 | 162.1, 89.5 | 86 | 14 | Y | ||||
| South Africa, 2011 [ | Societal | 509 | 491.4†, 1553.2‡ | 100 | |||||||
| South Africa, 2012 [ | Societal/health care | 745 | 1223.1 | 98 | 2 | 0.2 | |||||
| WPR | Fiji, 2012 [ | Societal/household | 390 | 25.7, 15.6 | 61.9 | 33.2 | 4.9 | ||||
| AMR | Colombia, 2013 [ | Healthcare | 1545 | 304.4 | 76.2 | ||||||
| EMR | Jordan, 2010 [ | NA | 728 | 563.4 | 100 | ||||||
| SEAR | Bangladesh, 2012* | Societal | 340 | 15.7 | |||||||
| Viet Nam, 2010 [ | Healthcare | 788 | 61.2 | ||||||||
| Pakistan, 2008 [ | Healthcare | 141 | 81.3 | ||||||||
| AFR | South Africa, 2011 [ | NA | 3014 | 849.0†
14795.4‡ | |||||||
| South Africa, 2012 [ | Societal/health care | 745 | 6696.2 | ||||||||
| AMR | Colombia [ | Healthcare | 1545 | 3643.4 | |||||||
NA – information not available, Y – authors considered the cost component, but the proportion was unknown, EUR – Europe Region, AMR – The Americas Region, WPR – Western Pacific Region, SEAR – South East Asia, AFR – The Africa Region, EMR – Eastern Mediterranean Region
*Unpublished data.
†Public health care.
‡Private health care.
§Pediatric ward.
#Supplementary health system.
Figure 3Range of cost per episode for pneumonia management (2013 US$).
Direct medical cost for severe pneumonia management in low– and middle–income countries reported from household perspective
| Country, publication year | Direct medical cost (2013 US$; % of direct medical cost to monthly household income) | Monthly household income (2013 $US) | ||||
|---|---|---|---|---|---|---|
| 124.2 (52.9%) | – | – | 234.9 | |||
| 80.6‡ (34.3%) | 62.6§ (26.6%) | 234.9 | ||||
| 305.8 (115.8%) | 135.1 (64.7%) | – | 264.0 | |||
| – | – | 7.9 (2.3%) | 1.5 (0.4%) | 338.3 | ||
| – | – | – | 2.7 (0.7%) | 398.6 | ||
| 25.7 (4.1%)/15.6 (2.5%) | 632.5‡ | |||||
*Monthly household income (2013 US$) were derived from Gallup World Poll annual median household income, equals annual median household income divided by 12. These results were based on Gallup data gathered between 2006 and 2012 in 131 population. Source: http://www.gallup.com/poll/166211/worldwide-median-household-income-000.aspx.
†Numbers used GNI per capita based on purchasing power parity (PPP) due to lack of monthly household income data. Source: http://data.worldbank.org/indicator/NY.GNP.PCAP.PP.CD/countries.
‡Public health care.
§Supplementary health system.
Direct non–medical cost and indirect cost per episode for severe pneumonia management in low– and middle–income countries
| Country, publication year | Direct non–medical cost* | Indirect cost† | % of non–medical cost to monthly household income | Monthly household income (2013 US$) | ||
|---|---|---|---|---|---|---|
| 32.4 | 13.8% | 234.9 | ||||
| 5.3 | 5.3 | 47.5 | 2.0% | 264.0 | ||
| 35.9 | 12.2 | 23.7 | 10.6% | 338.3 | ||
| 55.0 | 16.3% | 338.3 | ||||
| 3.3 | 2.3 | 1.0 | 9.6 | 1.0% | 338.3 | |
| 14.0 | 9.0% | 155.8 | ||||
| 30.0 | 31.0% | 96.7‡ | ||||
| 2.0 | 1.4 | 0.2 | 0.5% | 434.8 | ||
| 33.2 | 33.2 | 4.9 | 5.3% | 632.5‡ | ||
| 9.7 | 8.41 | 1.31 | 73.1 | 1.6% | 626.8 | |
CI – confidence interval, IQR – interquartile range
*Direct medical costs include medications and consultation, non–medical cost includes transportation, food and accommodation.
†Indirect cost refers to parental loss of earnings in the period of illness. Monthly household income (2013 US$) was derived from Gallup World Poll annual median household income, equals annual median household income divided by 12. These results were based on Gallup data gathered between 2006 and 2012 in 131 populations. Source: http://www.gallup.com/poll/166211/worldwide-median-household-income-000.aspx.
‡Numbers used GNI per capita based on purchasing power parity (PPP) due to lack of monthly household income data. PPP GNI is gross national income (GNI) converted to international dollars using purchasing power parity rates. An international dollar has the same purchasing power over GNI as a US dollar has in the United States. GNI is the sum of value added by all resident producers plus any product taxes (less subsidies) not included in the valuation of output plus net receipts of primary income (compensation of employees and property income) from abroad. Source: http://data.worldbank.org/indicator/NY.GNP.PCAP.PP.CD/countries.
Length of stay of very severe pneumonia and severe pneumonia in hospital in high–income countries
| Country and year | Setting | LOS (SD) days | Sample size |
|---|---|---|---|
| Germany, 2005 [ | ICU | 7.4 (6.1) | 2039 |
| Spain, 2013 [ | ICU | 18.0 | 99 |
| USA, 2012* | ICU | 18.3 (43.1) | 1116 |
| Australia, 2011* | ICU | 11.0 | – |
| Median (IQR) | 14.5 (10.1–18.1) | ||
| Ireland, 1999 [ | Control group | 8.3 (7.7–9.0) | 44 |
| New treatment group | 4.0 (3.5–4.6) | 45 | |
| Germany, 2005 [ | Hospitalised cases | 7.4 (6.1) | 2039 |
| Australia, 2008 [ | Without impact diary | 8.8 | 202 |
| With impact diary | 13.5 | 523 | |
| Australia, 2011* | Non–ICU | 6.0 | – |
| Spain, 2013 [ | Non–ICU | 10.5 | 99 |
| USA, 2012* | Non–ICU | 2.7 (2.3) | 940 |
IQR – interquartile range, ICU – intensive care unit
*Unpublished data.
Length of stay of severe pneumonia in hospital in low– and middle–income countries
| Country, year | Description | Length of stay (SD) in days‡ | Sample size |
|---|---|---|---|
| Probable pneumonia | 7.2 (5.0) | 40 | |
| Radiograph confirmed | 6.7 (3.8) | 426 | |
| Probable severe pneumonia | 6.2 (3.3) | 59 | |
| Radiograph confirmed severe pneumonia | 6.4 (2.7) | 193 | |
| Hospital care | 6.0 (5.0–7.0) | 180 | |
| Public health care | 7.1 | 73 | |
| Private health care | 6.4 | 41 | |
| Hospital stay | 7.0 (3.0)† | 93 | |
| Antibiotic use duration | Approx. 8 | 124 | |
| National hospitals | 8.2 | 49 | |
| District hospitals | 6.7 | 30 | |
| District hospitals | 4.8 | 29 | |
| District hospitals | 4.2 | 17 | |
| Provincial hospitals | 6.6 | 31 | |
| Mission Hospitals | 7.8 | 30 | |
| Mission Hospitals | 3.4 | 19 | |
| Tertiary health center | 4.0 | 221 | |
| Time spent at health facility for severe pneumonia | 3.3 | 65 | |
| Secondary hospital | 3.0 | 502 | |
| In–patient days | 4.0–5.0 | 728 | |
| Secondary hospital | 3.5 (2.9–4.1) | 31 | |
| Tertiary hospital | 3.7 (3.0–4.4) | 25 | |
| Tertiary hospital | 6.5 (2.5) | 52 | |
| Public health system | 3.9 (2.2) | 59 | |
| Supplementary health system | 5.3 (4.7) | 20 | |
| Primary | 2.0 (1.0–2.0) | 247 | |
| Secondary hospital | 4.0 (1.0–5.0) | 1208 | |
| Tertiary hospital | 6.0 (3.0–9.0) | 47 | |
| Public sector ward | 8.7 | 86 | |
| Fee for service sector | 5.6 | 7786 | |
| Paediatric ward | 8.1 (7.4–8.8) | 513 | |
| Non–ICU | 6.7 | – | |
| Severe pneumonia | 7.5(8.5) | 42 | |
| Unilateral focal pneumonia without complications | 7.4 (6.0) | 1994 | |
| Multifocal pneumonia without complications | 8.0 (6.5) | 323 | |
ICU – intensive care unit
*Unpublished data..
†Combined HIV+ and HIV–, HIV+ had longer stay in ward (9.3 vs 7.0 days)
‡Length of stay (LOS) reported as mean, mean (standard deviation) or median (interquartile range). When stratified LOS available, then stratified LOS was reported, not average length of stay of all pneumonia.
Length of stay of very severe and non–severe pneumonia in hospital in low– and middle–income countries
| Country, year | Description | Length of stay (SD) days | Sample size |
|---|---|---|---|
| Viet Nam, 2010 [ | Very severe pneumonia | 6.4(2.7) | 26 |
| Confirmed very severe pneumonia | 5.8 (3.0) | 44 | |
| Colombia, 2013 [ | ICU | 13.0 (6.0–14.0) | 43 |
| South Africa, 2011 [ | ICU | 9.4 | 46 |
| ICU | 10.5 | 93 | |
| South Africa, 2012 [ | ICU | 14.4(10.3–18.5) | 7 |
| Pakistan, 2008 [ | Time spend at health facility for very severe pneumonia | 3.9 | 35 |
| Argentina, 2012† | Very severe pneumonia | 8.9 | – |
| Unilateral focal pneumonia without complications | 17.2 | – | |
| Multifocal pneumonia without complications | 11.5 | – | |
| Brazil, 2011* | Public health system | 6.9 | – |
| Supplementary health system | 6 | – | |
| Median (IQR) | 9.2 (6.1–12.6) | ||
| Pakistan, 2008 [ | Time spend at health facility for pneumonia | 0.3 | 41 |
| South Africa, 2012 [ | Short stay | 1.4 (1.3–1.6) | 338 |
ICU – intensive care unit, IQR – interquartile range
*Unpublished data.
†Note added in proof: The data from this study are unpublished but the data on the length of stay are published in Giglio ND, Cane AD, Micone P, Gentile A. Cost-effectiveness of the CRM-based 7-valent pneumococcal conjugated vaccine (PCV7) in Argentina. Vaccine. 2010;28:2302-10. Medline:20064478.
Chest Radiography cost per episode
| Country, year | Cost per episode (2013 US$) | |
|---|---|---|
| Australia, 2011* | 129.8 | |
| Chile, 2007 [ | 135.1 | |
| Uruguay, 2007 [ | 43.4 | |
| United States, 2012* | 433.7 | |
| Argentina, 2012* | 26.7 | |
| Brazil, 2011* | 10.7 | |
| 6.0 | ||
| Brazil, 2007 [ | 13.63 | |
| Bangladesh, 2010* | 2.3 | |
| India, 2009 [ | 5.4 | |
| Pakistan, 2008 [ | 3.2 | |
| Indonesia, 2001* | 4.6 | |
| Kenya, 2009 [ | 2.3 | |
| South Africa, 2001* | 29.7 | |
| South Africa, 2011 [ | 59.7 | |
| 137.2 | ||
| South Africa, 2012 [ | 27.7 | |
*Unpublished data.
Characteristics of all studies included*
| WHO region | Country, publication year | Study population | Healthcare setting | Severity of pneumonia studied | Study design | Source of case definition | Perspective | Sample size | Mean (SD) /median age of patients (months) | Data source |
|---|---|---|---|---|---|---|---|---|---|---|
| EUR | Northern Ireland, 1999 [ | Antrim (urban) | H2 | S | QES | PD | N/A– | 45 | 39.60 (16.8) | H |
| Spain, 2013 [ | Barcelona (urban) | H3 | S, VS | Cost analysis‡ | Culture–proved pneumonia | Healthcare | 101 | 39.60 | H | |
| Germany, 2005 [ | National | O,H1 | S, VS | Cost–of–illness | PD | Societal | 402 | N/A | N, IQ | |
| AMR | Chile, Uruguay, 2007 [ | National | O,H1 | S, NS | Cost analysis‡ | PD, ICD–10 | Healthcare | 366 | N/A | H,IQ |
| United States, 2012* | Denver, Colorado (urban) | H3 | S, VS, NS | Cost–of–illness | PD by WHO IMCI definition | Societal | 940 | 0–59 | H, P | |
| WPR | Australia, 2008 [ | National | O, H1–3 | S | Cost analysis‡ | ICD–10 | Healthcare | 1348 | N/A | N |
| Australia, 2008 [ | Melbourne, Victoria (urban) | O,H1 | S | Cohort study/cost–of–illness | Health professional’s diagnosis | Societal | 528 | N/A | N,H,IQ, Pilot | |
| Australia, 2011* | Sydney (urban) | H3 | S, VS | Cost–of–illness | PD by WHO IMCI definition | Societal | N/A | N/A | P, Market price | |
| SEAR | Bangladesh, 2010 [ | Dhaka (urban) | H3 | S | Cost–of–illness | PD | Family | 90 | 5.00 | IQ |
| Bangladesh, 2005† | Dhaka (urban) | H3 | S, VS | Cost–of–illness | PD by WHO IMCI definition | Household | 114 | 70.32 | IQ | |
| Bangladesh, 2010 [ | Mirpur, Dhaka (urban) | O, H2 | S | RCT/CEA | PD by WHO IMCI definition | Societal | 360 | 8.00 | – | |
| Bangladesh, 2010† | Barishal, Bogra, Comilla, Kishoregonj (urban) | H3 | S, NS | Cost–of–illness | PD by WHO IMCI definition | Societal | 235 | N/A | IQ | |
| Bangladesh, 2012† | Mohakhali, Dhaka (urban) | H3 | S, VS, NS | Cost–of–illness | PD by WHO IMCI definition | Societal | 340 | N/A | H | |
| India, 2009 [ | Vellore (rural) | H1, H2 | S | Cost–of–illness | PD by WHO IMCI definition | Healthcare/ Household | 56 | 8.8 | H, IQ | |
| India, 2002 [ | Berhampur, Orissa (urban and rural) | H3 | S | Epidemiological study | PD | Societal | 52 | N/A | H, IQ | |
| Indonesia, 2001† | Lombok (rural) | H3 | S | Cost–of–illness | PD by WHO IMCI definition | Societal | N/A | N/A | H | |
| Pakistan, 2003 [ | Peshawar city (urban) | H3 | S | RCT/CEA | PD by WHO IMCI definition | – | 126 | N/A | – | |
| Pakistan, 2006 [ | Ghizer district (rural) | O, H1, H2 | S, NS | Cost analysis‡ | PD | Societal | 502 | N/A | IQ | |
| Pakistan, 2008 [ | Ghizer district (rural) | O, H1, H2 | S, VS, NS | Cost analysis‡ | PD by WHO IMCI definition | Healthcare | 141 | N/A | IQ | |
| Pakistan, 2010† | Matiari (rural) | C | S | Cost–of–illness | PD by WHO IMCI definition | Healthcare | N/A | N/A | Surveillance | |
| Pakistan, 2012 [ | Haripur district (rural) | C, H1, H2 | S | Cost analysis‡ | WHO definition by health worker | Household | 423 | N/A | H, IQ | |
| Viet Nam, 2010 [ | Nha Trang city (urban) | H2 | S, VS, NS | Cost–of–illness | PD by WHO IMCI definition | Healthcare | 788 | 12.67 | N, H | |
| Viet Nam, 2001 [ | Ba Vi district (rural) | C, O, H1 | S | Cost analysis‡ | WHO definition, self–reported | Household | 94 | N/A | IQ | |
| AFR | Guinea, 1998 [ | National | O, H1 | S, NS | CEA | PD | – | 73650 | N/A | H, E |
| South Africa, 2011 [ | Pretoria (urban) | H3 | S, VS | Cost analysis‡ | WHO definition | – | 3014 | N/A | H | |
| South Africa, 2012 [ | National | H3 | S, VS, NS | RCT | PD | Societal/health care | 745 | N/A | H, IQ | |
| South Africa, 2001† | Soweto (urban) | H3 | S, VS | Cost–of–illness | PD by WHO IMCI definition | Societal | 509 | 14.00 | H,IQ | |
| Kenya, 2009 [ | National | H3, H2, H1 | S | Cost analysis‡ | PD | Societal | 205 | 12.00 | H, IQ | |
| Zambia, 2009 [ | Kanyama Township (urban) | O,H2 | S | Cost analysis‡ | PD | Healthcare | 9146 | N/A | N,H,P,W | |
| AMR | Colombia, 2013 [ | National | H1,H2,H3 | S, VS, NS | Cost–of–illness§ | WHO definition, radiographically diagnosed | Healthcare | 1545 | N/A | I |
| Brazil, 2011† | Goiânia (urban) | H3 | S, VS | Cost–of–illness§ | PD by WHO IMCI definition | Societal | 79 | 0–36 | H, N | |
| Argentina, 2012† | Buenos Aires (urban) | H3 | S, VS | Cost–of–illness§ | PD by WHO IMCI definition | Societal | N/A | N/A | N | |
| Brazil,2007 [ | National | O,H1 | S, NS | Cost analysis‡ | PD, ICD–10 | Healthcare | 366 | N/A | H,IQ | |
| WPR | Fiji, 2012 [ | Viti Levu (urban and rural) | O | S | Cost analysis‡ | PD by WHO IMCI definition | Societal/household | 390 | N/A | N,H, IQ |
| EMR | Jordan, 2010 [ | Amman | H1 | S | Cohort study | PD | – | 728 | 4.30 | N/A |
*Severity of pneumonia: NS – non severe, S – severe, VS – very severe. Data source: H – hospital records, N – national data, IQ – interviews and questionnaires, I – insurance database, P – pharmacy database, W – WHO database. Treatment settings: H3 – tertiary hospital in–patient, H2–secondary hospital in–patient, H1 – primary hospital inpatient, O – out–patient care, C – community ambulatory care; PD – physician’s diagnosis, CEA – cost effectiveness analysis, RCT – randomized clinical trial, QES– quasi–experimental study, N/A – not available, PD – physician’s diagnosis, IMCI – Integrated Management of Childhood Illness, WHO – World Health Organization, SD – standard deviation.
EUR – Europe Region, AMR – the Americas Region, WPR – Western Pacific Region, SEAR – South East Asia, AFR– The Africa Region, EMR– Eastern Mediterranean Region
†Unpublished data.
‡The analysis of the comparative costs of alternative treatments or health care programmes.
§The cost analysis of treatment of a disease.