Library Guides: Systematic Reviews for Health Sciences and Medicine: Common search errors

Example: Search for Sub-Saharan Africa

A researcher is looking for studies from sub-saharan Africa and uses the 2 search lines below in Medline (Ovid).

The first line searches for primary concepts
The second line searches for individual nations that make up the area
The third line combines the search results.

This appears to follow best practice but has a number of commonly seen errors that can reduce the value of a search strategy.

Line	Terms
1	sub-saharan africa or east* africa or west* africa or southern africa or central africa
2	Angola* or Benin or Botswana* or Burkina Faso or Burundi* or Cameroon* or Cape Verde* or Central African Republic or Chad* or Comoro* or Democratic Republic of the Congo or Congo* or Cote d'Ivoire or Djibouti or Equatorial Guinea* or Guinea-Bissau or Eritrea* or Ethiopia* or Gabon* or Gambia* or Ghana* or Guinea* or Kenya* or Lesotho or Liberia* or Madagascar or Malagasy or Malawi* or Mali* or Mauritania* or Mauritius or Mozambi* or Namibia* or Niger* or Nigeria* or Rwanda* or Sao Tome and Principe or Senegal* or Seychelles* or Sierra Leone* or Somalia* or South Africa* or Swaziland* or Sudan* or Tanzania* or Western Sahara or Togo* or Uganda* or Zambia* or Zimbabwe*
3	1 or 2

This search has 6 common search errors, solved below.

Common search errors

Problem

Sao Tome and Principe is not enclosed in quotation marks.
This means the AND is interpreted as part of the search.

((Angola* or Benin or Botswana* or Burkina Faso or Burundi* or Cameroon* or Cape Verde* or Central African Republic or Chad* or Comoro* or Democratic Republic of the Congo or Congo* or Cote d'Ivoire or Djibouti or Equatorial Guinea* or Guinea-Bissau or Eritrea* or Ethiopia* or Gabon* or Gambia* or Ghana* or Guinea* or Kenya* or Lesotho or Liberia* or Madagascar or Malagasy or Malawi* or Mali* or Mauritania* or Mauritius or Mozambi* or Namibia* or Niger* or Nigeria* or Rwanda* or Sao Tome) and Principe) or Senegal* or Seychelles* or Sierra Leone* or Somalia* or South Africa* or Swaziland* or Sudan* or Tanzania* or Western Sahara or Togo* or Uganda* or Zambia* or Zimbabwe*

Results will include the countries up to Sao Tome (in yellow) only if the word Principe appears as well.
Results will include all the later countries (in pink). This is a large set of records including countries such as South Africa, Sudan and Zimbabwe.
This is difficult to identify as the result set is still large and seems to have worked correctly.

Solution

add quotation marks around phrases containing OR, AND or NOT
"Sao Tome and Principe"

In the Ovid database platform the terms SUB, USE and ROOT are also command terms that require quotation marks
"sub saharan"
If in any doubt, add quotation marks to all phrases
In most database systems including Ebsco, Web of Science, Scopus and Proquest, search lines with OR and phrases without quotation marks will result in failures.

This is the most problematic error as it is does not return all of the search terms in a group, so is therefore hard to identify.
Avoid this error first!

Problem

Many of the country names have been truncated to return their plural form and population groups.
Mali* returns malignant, malignancy and malignancies, key terms for cancer literature

Solution

Test terms one at a time in the database before combining lots of them.
Mali* has more than 600 000 items whereas Angola* has 2000 items. It is evident there is an issue that needs investigating.
To identify other irrelevant terms, search for the truncated term and individual terms you are expecting
Then remove the individual terms with NOT

Line	Terms
1	Mali*
2	Mali or Malis or Malian
3	1 not 2

These errors can introduce thousands of irrelevant results to the final result and cause extra weeks or months screening unnecessary items.

Problem:

Search terms may have multiple meanings.
In some cases, the other meanings are not relevant to other parts of the search and are therefore not a significant issue.
However, you should be aware of what impact each term could have and determine whether its alternative meanings could be eliminated.
Guinea* also returns guinea pig, a significant research animal, and Papua New Guinea, a country not within Sub-Saharan Africa.

Solution:

Search for Guinea in a separate line excluding the other forms.
Guinea* not ("Papua New Guinea*" or "guinea pig" or "guinea pigs")

These errors can introduce significant numbers of irrelevant items to final results. If you see lots of unrelated items in your final result set check for this issue

Problem:

This search does not include subject headings
In Medline the subject heading for Sub-Saharan Africa is "Africa South of the Sahara"
This term has narrower terms including regional terms "Africa, Central", "Africa, Eastern", "Africa, Southern", "Africa, Western" and a listing of all the countries in each region.

Solution:

To fix this, search for your concept terms with the Subject Heading Map function in the database you are using to check if alternative terms are used and see if there is a function to search for narrower headings at the same time.
In Medline (Ovid) you can explode a subject heading, meaning you can search for all the terms underneath
Adding an exploded subject heading improves this search strategy significantly.
exp "Africa South of the Sahara"/

This error can impact on the results of the published review being taken as a good attempt to identify all relevant literature.
It's impact depends on how much literature is missed by not using the most appropriate subject term for the database.

Problem

The search includes sub-saharan africa.
Phrases including dashes do not automatically search for variants that do not have the dash. Usually a dash is treated as a space although when entered with quotation marks, forms with the space can be excluded.
In this case, sub-saharan refers to nothing other than Africa so Africa can be eliminated to return other phrases like sub-saharan population, sub-saharan nations or sub-saharan communities.

Solution:

Include all variations within quotation marks.
"sub-sahara*" or "sub sahara*" or "subsahara*"

This error will usually mean at least some relevant literature is missed. Never assume a term is always entered one way or the other - researchers always use every variant.

Problem:

Terms that are included by themselves do not have to be repeated in phrases.
This error doesn't improve the search but can simplify it in many cases.

Solution:

Niger* returns both Niger, Nigeria, Nigerian and Nigerians
Congo* returns Congo, Democratic Republic of the Congo, Congolese and Congos
Guinea* returns Guinea, Equatorial Guinea and Guinea-Bissau

This has no impact but can result in your search strategy being hard to interpret with overuse of redundant phrases.

Example: Search for Sub-Saharan Africa (revised)

Here is an improved version for Sub-Saharan Africa for Medline (Ovid). Searches in other databases would need an appropriate subject search in line 2.

Line	Search Terms
1	"sub-sahara" or "sub sahara" or subsahara* or ((east* or west or central or southern) adj2 africa)
2	exp "Africa South of the Sahara"/
3	Angola* or Benin or Botswana* or "Burkina Faso" or Burundi* or Cameroon* or "Cape Verde" or "Central African Republic" or Chad or Comoro* or Congo* or "Cote d'Ivoire" or Djibouti or Eritrea* or Ethiopia* or Gabon* or Gambia* or Ghana* or Kenya* or Lesotho or Liberia* or Madagascar or Malagasy or Malawi* or Mauritania* or Mauritius or Mozambi* or Namibia* or Niger* or Rwanda* or "Sao Tome and Principe" or Senegal* or Seychelles* or "Sierra Leone" or Somalia or "South Africa" or Swaziland or Sudan* or Tanzania* or "Western Sahara" or Togo* or Uganda* or Zambia* or Zimbabwe*
4	Mali or Malis or Malian
5	Guinea* not ("papua new guinea*" or "guinea pig" or "guinea pigs")
6	1 or 2 or 3 or 4 or 5

Africa map created by SVGrepo