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AIDS. Case Definition. Epidemological Bulletin, June 2001.

http://www.paho.org/English/SHA/be_v22n2-SIDA.htm

from Epidemiological Bulletin, Vol. 22 No. 2, June 2001

Case Definition
Acquired Immunodeficiency Syndrome (AIDS)

Rationale for surveillance
AIDS is a disease targeted for reduced incidence, prevalence and transmission (9GPW, target 6.3). Control measures are based on prevention and care strategies. Surveillance is necessary to assess national needs in education, supplies, and health care and to anticipate spread in the community. Surveillance will provide epidemiological data used for national prevention and care plan and will be essential to evaluate the impact of control activities.

Recommended case definitions
Different case definitions are used in different countries, depending on population factors (children, adults, relative occurrence of opportunistic infections) and on the laboratory infrastructure and training available. Current case definitions include: (1-3: for sophisticated laboratory facilities; 4-6 for limited laboratory facilities)

(1) CDC 1987; (2) CDC/CD4; (3) European; (4) WHO for surveillance (formerly Bangui/WHO/clinical); (5) Expanded WHO for surveillance (formerly Abidjan);
(6) Caracas/PAHO & revised Caracas/PAHO.

1. 1987 CDC Surveillance definition for AIDS (1)
1A Without laboratory evidence of HIV infection (no other causes of immune suppression)
Indicator disease diagnosed definitively

1B. With laboratory evidence of HIV infection
Indicator disease diagnosed definitively

2. Conditions added to CDC surveillance definition for AIDS with laboratory evidence of HIV infection (1B above) (2)
In addition to those in the surveillance definition:

3. European AIDS case definition (3)
Same as revised CDC definition (2 above) without CD4+ T-lymphocyte count.

4. WHO Case definition for AIDS surveillance (formerly Bangui/WHO/Clinical) (5)
WHO clinical case definition for AIDS in an adult or adolescents (>12 years of age) when diagnostic resources are limited. For the purposes of AIDS surveillance an adult or adolescent (>12 years of age) is considered to have AIDS if at least 2 of the following major signs are present in combination with at least 1 of the minor signs listed below, and if these signs are not known to be related to a condition unrelated to HIV infection.

Major signs (2 signs or more):

Minor signs (1 or more):

The presence of either generalized Kaposi sarcoma or cryptococcal meningitis is sufficient for the diagnosis of AIDS for surveillance purposes.

5. Expanded WHO case definition for AIDS surveillance (formerly Abidjan) (4)
For the purpose of epidemiological surveillance, an adult (>12 years of age) is considered to have AIDS if a test for HIV antibody shows positive results, and one or more of the following are present:

6. Revised Caracas/PAHO AIDS Definition (6,7)
A patient is defined as having AIDS when:
- cumulative points assigned for conditions listed hereafter equal or exceed 10, and
- HIV serology is positive.

Cases in which the total point score equals or exceeds the required score of 10, but HIV serology is pending are considered Òprovisional casesÓ. Persons with cancer, or with immunosuppressive therapies, or where the sign / symptoms are attributed to conditions other than HIV infection are excluded.

Symptoms/signs/diagnostic Assigned points
- Kaposi sarcoma 10
- Disseminated / extrapulmonary / non-cavity pulmonary tuberculosis 10
- Oral candidiasis / hairy leukoplasia 5
- Pulmonary tuberculosis with cavitation, or unspecified 5
- Herpes zoster in a person of 60 years or less 5
- Central nervous system dysfunction 5
- Diarrhea one month or more 2
- Fever of at least 38oC for at least a month 2
- Cachexia or weight loss of more than 10% 2
- Asthenia of at least a month 2
- Persistent dermatitis 2
- Anaemia, lymphopenia, and/or thrombocytopenia 2
- Persistent cough or any pneumonia, and/or thrombocytopenia 2
- Lymphadenopathy of at least 1cm at at least two non-inguinal sites 2
Required point score 10 or more

Case classification
Depends on the case definition. Please check with National AIDS programmes.

Recommended types of surveillance
Routine monthly reporting of aggregated data from periphery to intermediate level.

Routine quarterly reporting of aggregated data from intermediate level to central level.

International: report updates every 12 months in the Weekly Epidemiological Record

Other sources of data:
- Hospitals
- Practitioners
- Consultations for sexually transmitted diseases (STD)
- Tuberculosis wards
- Mortality reports and statistics
- Active case finding.

Recommended minimum data elements
Case-based data for reporting
Unique identifier, age, sex, geographical area, mode of transmission (e.g., blood transfusion, drug use, other).

Aggregated data for reporting
Number of cases by age and sex, number of cases, mode of transmission (e.g., blood transfusion, drug use, other).

Recommended data analyses, presentation, reports
Graphs: Number of cases by age, sex, geographical area, risk factors.
Tables: Number of cases by age, sex, geographical area, risk factors.
Maps: Number of cases by geographical area.

Principal uses of data for decision-making
- Assess the magnitude of the problem
- Identify high risk areas for further intervention
- Plan public health measurements
- Assess impact on clinical services
- Plan health care services and supplies
- Validate HIV surveillance data

References
(1) MMWR Aug. 14, 1987/Vol. 36(suppl.)1-15s
(2) MMWR May 2, 1997/Vol. 46/No. RR-10
(3) Lancet, 1993;341:441 and AIDS Surveillance in Europe, Quarterly Report, 1993 ;number 37
(4) AIDS 1993, Vol. 7 (suppl 1)
(5) AIDS 1993, Vol. 7 (suppl 1)
(6) Epidemiological Bulletin of PAHO Vol. 10 # 4 1990 Working group on AIDS case definition pages 9-11 o Journal of Acquired Immune Deficiency Syndrome Vol. 5 # 12 1992 Ò A simplified surveillance case definition of AIDS derived from empirical clinical dataÓ.
(7) AIDS 1993, Vol. 7 (suppl 1)

Source: "WHO Recommended Surveillance Standards, Second edition, October 1999: , WHO/CDS/CSR/ISR/99.2

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Epidemiological Bulletin, Vol. 22 No. 2, June 2001