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Constructing a literature search for a systematic review: part 3, putting your search terms together and testing their efficiency

This is the third in a series of posts looking at how to put together a literature search for a systematic review. Part 1 looked at the preparation required before you start putting the search together and gives some background to the project and part 2 looked at how to put together a list of search terms. As it’s been a few weeks since those were published, you might want to have a little look to remind yourself of the project. This part looks at how to string your terms together and test their impact on the results you retrieve.

I am not going to go step-by-step through each concept, as I did in part 2, instead I will describe some of the techniques I use.

Why test your terms?

If you test your terms and try to figure out the contribution they make to the overall search, you can get some idea of how relevant the terms are to the overall search. This also gives you an idea of whether a particular term is ambiguous, ie it is used in more than one context so is likely to return irrelevant results. The purpose is not to give a definitive view of the number of unique references each term contributes to the total number of retrieved results, but to make sure the search is both comprehensive and efficient. Testing your terms allows you to create a search which is as specific and yet sensitive as required.

How I test my terms

Testing individual terms

This is a technique I have refined over the years. I’d be really interested to hear from anyone else who has any other tips and tricks for how to do this.

I start with a list of terms. For example:

Gender inequality/inequity/equality
Gender based inequality
Gender discrimination
Gender-related reasons
Gender relations*
Women adj? social status
Gender* power
Gender norms
Gender roles
Gender-related risk
Gender issues
Relationship dependency
Positive action?
Gender disparity/disparities
Gender sensitive/sensitivity
Social construction of gender
Gender-centred
Gender bias
Gender awareness
Gender differences
Gender imbalance

I noticed that lots of these phrases had the word ‘gender’ in them. I decided to test whether entering only ‘gender’ would result in the return of a large number of irrelevant articles. The advantage of this would be that I wouldn’t have to include all of phrases which might be in the literature (as listed above) and it would save me time as I would not have to try to put together a comprehensive list of phrases. Entering ‘gender*.ti,ab.’ into Ovid Medline gives me 251,970 results, which is way too many to look at to see how the word contributes to my specific search. Therefore I combined it with the MeSH terms for the other concepts. So I constructed this quick search:

  1. child/ or adolescent/ or young adult/
  2. exp “Africa South of the Sahara”/
  3. exp HIV Infections/ or exp HIV/
  4. gender*.ti,ab.
  5. and/1-4

I had a look at the first 50 results this retrieved to see how relevant they were. They were not all relevant, but most of them were. Therefore, I decided to use the more general term.

I did this level of analysis for the other words and phrases I had put together in part 2.

Determining proximity

Often, using a general term to capture a large number of phrases is not viable and in these cases proximity searching is a useful tool. This allows us to search for words which appear close to each other in the text, but not necessarily next to each other. Most databases which offer this feature allow you to specify the maximum number of words which might occur between your required terms. So some testing is necessary to determine the most efficient proximity to use.

To do this, I run a series of searches, increasing the size of the proximity operator each time, then using the Boolean operator NOT to view the references retrieved only by the change.

As an example, I put together the following search:

  1. child/ or adolescent/ or young adult/
  2. exp “Africa South of the Sahara”/
  3. exp HIV Infections/ or exp HIV/
  4. ((financial or cash or pay* or monetary or money or economic or financial) adj1 (transfer* or measure* or
    incentive* or allowance* or exclu* or reform* or gain* or credit or credits or benefit or benefits or support)).ti,ab.
  5. ((financial or cash or pay* or monetary or money or economic or financial) adj2 (transfer* or measure* or
    incentive* or allowance* or exclu* or reform* or gain* or credit or credits or benefit or benefits or support)).ti,ab.
  6. ((financial or cash or pay* or monetary or money or economic or financial) adj3 (transfer* or measure* or
    incentive* or allowance* or exclu* or reform* or gain* or credit or credits or benefit or benefits or support)).ti,ab.
  7. ((financial or cash or pay* or monetary or money or economic or financial) adj4 (transfer* or measure* or
    incentive* or allowance* or exclu* or reform* or gain* or credit or credits or benefit or benefits or support)).ti,ab.
  8. ((financial or cash or pay* or monetary or money or economic or financial) adj5 (transfer* or measure* or
    incentive* or allowance* or exclu* or reform* or gain* or credit or credits or benefit or benefits or support)).ti,ab.
  9. ((financial or cash or pay* or monetary or money or economic or financial) adj6 (transfer* or measure* or
    incentive* or allowance* or exclu* or reform* or gain* or credit or credits or benefit or benefits or support)).ti,ab.
  10. and/1-4
  11. and/1-3,5
  12. and/1-3,6
  13. and/1-3,7
  14. and/1-3,8
  15. and/1-3,9
  16. 11 not 10
  17. 12 not 11
  18. 13 not 12
  19. 14 not 13
  20. 15 not 14

By examining the results on search lines 16 to 20 I can decide which is the most effective proximity search value to use.

My completed first draft search

Below is the first draft of the search I put together in Ovid Medline.

1 (structur* adj1 (driver* or intervention*)).ti,ab. (913)
2 Sex Workers/ (1515)
3 Sex Work/ (5847)
4 sex* work*.ti,ab. (4848)
5 prostitut*.ti,ab. (3584)
6 sex* industr*.ti,ab. (247)
7 escort*.ti,ab. (1074)
8 (sex* adj3 (buy* or commerc*)).ti,ab. (1882)
9 brothel*.ti,ab. (398)
10 (sex* adj5 (mone* or gift* or transaction* or exchange)).ti,ab. (1485)
11 (relations* adj5 transaction*).ti,ab. (155)
12 or/2-11 (12671)
13 exp Alcohol Drinking/ (63011)
14 ((alcohol* or beer or wine or lager or spirit* or drink) adj3 (consum* or unit* or purchas* or use* or intake or
binge)).ti,ab. (81770)
15 drink* rate*.ti,ab. (306)
16 drunk*.ti,ab. (3815)
17 or/13-16 (113052)
18 exp Intimate Partner Violence/ (8183)
19 Domestic Violence/ (5905)
20 Rape/ (6315)
21 Battered Women/ (2610)
22 Stalking/ (161)
23 intimate partner violence.ti,ab. (4361)
24 ipv.ti,ab. (3876)
25 rape*.ti,ab. (9076)
26 (sex* adj3 (aggress* or assault* or attack* or violen* or victimi#ation or revictimi#ation or
re-victimi#ation)).ti,ab. (9650)
27 (batter* adj3 wom#n).ti,ab. (752)
28 ((gender or peer) adj3 violence).ti,ab. (1025)
29 ((date or dating) adj3 (abuse* or abusive or aggress* or assault* or attack or coerc* or injur* or manipulat* or
rape* or violen*)).ti,ab. (1696)
30 ((relationship* or partner* or acquaintance* or non-stranger* or nonstranger*) adj3 (abuse* or abusive or
aggress* or assault* or attack or coerc* or injur* or manipulat* or rape* or violen*)).ti,ab. (11220)
31 ((spous* or husband* or wife* or co-habit* or married or marriage or bride or groom) adj3 (abuse* or abusive or
aggress* or assault* or attack or coerc* or injur* or manipulat* or rape* or violen*)).ti,ab. (1308)
32 ((boyfriend* or boy-friend* or girlfriend* or girl-friend*) adj3 (abuse* or abusive or aggress* or assault* or
attack or coerc* or injur* or manipulat* or rape* or violen*)).ti,ab. (36)
33 stalking.ti,ab. (524)
34 stalker*.ti,ab. (199)
35 or/18-34 (39928)
36 Sex Factors/ (248909)
37 exp Gender Identity/ (18542)
38 Women’s Rights/ (8427)
39 Feminism/ (1989)
40 Social Justice/ (11555)
41 gender*.ti,ab. (237823)
42 ((man or men or wom#n or sex or femini* or masculin* or relations*) adj3 role*).ti,ab. (11098)
43 or/36-42 (471511)
44 exp Poverty/ (38446)
45 socioeconomic factors/ (141289)
46 medical indigency/ (3578)
47 unemployment/ (6339)
48 employment/ (43143)
49 maternal welfare/ (6808)
50 public policy/ (30498)
51 social welfare/ (9147)
52 social security/ (7422)
53 (economic* adj2 (empower* or factor* or barrier* or freedom)).ti,ab. (5680)
54 economic abuse.ti,ab. (31)
55 (access adj3 money).ti,ab. (53)
56 remittance*.ti,ab. (436)
57 voucher*.ti,ab. (1335)
58 food stamp*.ti,ab. (316)
59 reimburse*.ti,ab. (20431)
60 ((prepayment or pre-payment) adj2 (plan* or scheme*)).ti,ab. (140)
61 ((demand-side or results-based) adj2 financing).ti,ab. (43)
62 output-based aid.ti,ab. (9)
63 ((financial or cash or pay* or monetary or money or economic or financial) adj3 (transfer* or measure* or
incentive* or allowance* or exclu* or reform* or gain* or credit or credits or benefit or benefits or support)).ti,ab.
(22985)
64 livelihood support.ti,ab. (18)
65 ((social or health or community) adj2 (insurance or security or welfare)).ti,ab. (45424)
66 ((child or family or maternity) adj2 (benefit* or allowance)).ti,ab. (967)
67 poverty.ti,ab. (17985)
68 low-income.ti,ab. (23634)
69 wealth.ti,ab. (12761)
70 employment.ti,ab. (42827)
71 unemployment.ti,ab. (8065)
72 employed.ti,ab. (239028)
73 unemployed.ti,ab. (6445)
74 (asset* adj3 ownership).mp. [mp=title, abstract, original title, name of substance word, subject heading word,
keyword heading word, protocol supplementary concept word, rare disease supplementary concept word, unique identifier,
synonyms] (116)
75 “standard of living”.ti,ab. (1105)
76 or/44-75 (616110)
77 1 or 12 or 17 or 35 or 43 or 76 [STRUCTURAL BARRIERS] (1165365)
78 Child/ (1598598)
79 Adolescent/ (1905520)
80 Young adult/ (646589)
81 exp Child welfare/ (30448)
82 Child, abandoned/ (515)
83 exp Child, exceptional/ (847)
84 Child, orphaned/ (616)
85 Child hospitalized/ (6359)
86 Child institutionalized/ (1870)
87 Adolescent hospitalized/ (425)
88 Adolescent institutionalized/ (123)
89 homeless youth/ (1158)
90 Minors/ (2514)
91 Students/ (48632)
92 Disabled children/ (5524)
93 child*.ti,ab. (1132843)
94 boy*.ti,ab. (126935)
95 girl*.ti,ab. (121928)
96 (schoolage* or (school adj1 age*)).ti,ab. (17166)
97 schoolchild*.ti,ab. (11922)
98 prepubescen*.ti,ab. (855)
99 pubescen*.ti,ab. (1651)
100 adolescen*.ti,ab. (206752)
101 juvenil*.ti,ab. (66653)
102 underage*.ti,ab. (881)
103 (teen or teens).ti,ab. (8370)
104 teenage*.ti,ab. (17500)
105 (youth or youths).ti,ab. (49372)
106 (transition adj4 adult*).ti,ab. (2757)
107 early adult*.ti,ab. (5285)
108 emerging adult*.ti,ab. (1156)
109 young adult*.ti,ab. (69912)
110 young person.ti,ab. (767)
111 young people.ti,ab. (19536)
112 child*.jw. (132699)
113 adolescen*.jw. (33558)
114 youth*.jw. (1614)
115 school*.jw. (16323)
116 or/78-115 [ADOLESCENTS] (3473581)
117 exp HIV/ (93993)
118 exp HIV Infections/ (267375)
119 hiv.ti,ab. (260587)
120 “hiv1”.ti,ab. (799)
121 “hiv2”.ti,ab. (156)
122 “hiv type 1”.ti,ab. (3762)
123 “hiv type 2”.ti,ab. (180)
124 human immunodeficiency virus.ti,ab. (76090)
125 human immunedeficiency virus.ti,ab. (4)
126 human immuno-deficiency virus.ti,ab. (205)
127 human immune-deficiency virus.ti,ab. (290)
128 (human immun* adj3 deficiency virus).ti,ab. (499)
129 acquired immunodeficiency syndrome.ti,ab. (15244)
130 acquired immunedeficiency syndrome.ti,ab. (10)
131 acquired immuno-deficiency syndrome.ti,ab. (111)
132 acquired immune-deficiency syndrome.ti,ab. (5338)
133 (acquired immun* adj3 deficiency syndrome).ti,ab. (5488)
134 or/117-133 [HIV] (352040)
135 Benin/ (1323)
136 (Benin or Dahomey).ti,ab. (2576)
137 Burkina Faso/ (2839)
138 (Burkina Faso or Burkina Fasso or Upper Volta).ti,ab. (3172)
139 Burundi/ (610)
140 Burundi.ti,ab. (634)
141 Central African Republic/ (728)
142 (Central African Republic or Ubangi-Shari).ti,ab. (816)
143 Chad/ (633)
144 Chad.ti,ab. (875)
145 Comoros/ (264)
146 (Comoros or Comoro Islands or Mayotte or Iles Comores).ti,ab. (443)
147 “Democratic Republic of the Congo”/ (3679)
148 ((democratic republic adj2 congo) or belgian congo or zaire).ti,ab. (3493)
149 Eritrea/ (263)
150 Eritrea.ti,ab. (350)
151 Ethiopia/ (9687)
152 Ethiopia.ti,ab. (8506)
153 Gambia/ (2372)
154 Gambia.ti,ab. (2030)
155 Guinea/ (883)
156 (Guinea not (New Guinea or Guinea Pig* or Guinea Fowl)).ti,ab. (3055)
157 Guinea-Bissau/ (873)
158 (Guinea-Bissau or Portuguese Guinea).ti,ab. (867)
159 Liberia/ (1045)
160 Liberia.ti,ab. (1111)
161 Madagascar/ (3006)
162 (Madagascar or Malagasy Republic).ti,ab. (3579)
163 Malawi/ (4349)
164 (Malawi or Nyasaland).ti,ab. (4652)
165 Mali/ (2145)
166 Mali.ti,ab. (2691)
167 Mozambique/ (1964)
168 (Mozambique or Portuguese East Africa).ti,ab. (2409)
169 Niger/ (1062)
170 (Niger not (Aspergillus or Peptococcus or Schizothorax or Cruciferae or Gobius or Lasius or Agelastes or
Melanosuchus or radish or Parastromateus or Orius or Apergillus or Parastromateus or Stomoxys)).ti,ab. (2501)
171 Rwanda/ (1965)
172 (Rwanda or Ruanda).ti,ab. (1994)
173 Senegal/ (5304)
174 senegal.ti,ab. (4603)
175 Sierra Leone/ (1269)
176 Sierra Leone.ti,ab. (1463)
177 Somalia/ (1397)
178 Somalia.ti,ab. (1033)
179 South Sudan/ (57)
180 south sudan.ti,ab. (282)
181 Tanzania/ (9904)
182 (Tanzania or Zanzibar).ti,ab. (9392)
183 Togo/ (996)
184 (Togo or Togolese Republic).ti,ab. (1109)
185 Uganda/ (10326)
186 Uganda.ti,ab. (9874)
187 Zimbabwe/ (5435)
188 (Zimbabwe or Rhodesia).ti,ab. (4830)
189 Cameroon/ (4768)
190 Cameroon.ti,ab. (4954)
191 Cape Verde/ (152)
192 (Cape Verde or Cabo Verde).ti,ab. (439)
193 Congo/ (1649)
194 (congo not ((democratic republic adj3 congo) or congo red or crimean-congo)).ti,ab. (2070)
195 Cote d’Ivoire/ (2874)
196 (Cote d’Ivoire or Ivory Coast).ti,ab. (3080)
197 Ghana/ (6550)
198 (Ghana or Gold Coast).ti,ab. (6649)
199 Kenya/ (14067)
200 kenya.ti,ab. (13101)
201 Lesotho/ (373)
202 (Lesotho or Basutoland).ti,ab. (509)
203 Mauritania/ (401)
204 Mauritania.ti,ab. (482)
205 Nigeria/ (26312)
206 Nigeria.ti,ab. (20104)
207 Atlantic Islands/ (734)
208 (sao tome adj2 principe).ti,ab. (104)
209 Sudan/ (4528)
210 (Sudan not south sudan).ti,ab. (5923)
211 Swaziland/ (466)
212 Swaziland.ti,ab. (611)
213 Zambia/ (3954)
214 (Zambia or Northern Rhodesia).ti,ab. (3820)
215 Angola/ (853)
216 Angola.ti,ab. (1013)
217 Botswana/ (1538)
218 (Botswana or Bechuanaland or Kalahari).ti,ab. (1796)
219 Equatorial Guinea/ (228)
220 (Equatorial Guinea or Spanish Guinea).ti,ab. (334)
221 Gabon/ (1368)
222 (Gabon or Gabonese Republic).ti,ab. (1413)
223 Mauritius/ (512)
224 (Mauritius or Agalega Islands).ti,ab. (724)
225 Namibia/ (893)
226 Namibia.ti,ab. (1012)
227 South Africa/ (37567)
228 South Africa.ti,ab. (23223)
229 Seychelles/ (330)
230 Seychelles.ti,ab. (538)
231 “africa south of the sahara”/ or africa, central/ or africa, eastern/ or africa, southern/ or africa, western/
(18745)
232 (“africa south of the sahara” or sub-saharan africa or central africa or eastern africa or southern africa or
western africa).ti,ab. (19782)
233 or/135-232 [SUB-SAHARAN AFRICA] (218039)
234 77 and 116 and 134 and 233 (5134)

I sent a copy of this, plus a link to an EndNote library containing the 5134 papers to the rest of the project team for discussion and possible edits. The editing process will be covered in part 4.

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