VACS Index 1.0: how the HIV mortality index points add up
The VACS Index 1.0 adds points for seven items in a person with HIV on antiretroviral drugs (ART): age, CD4 count, HIV-1 RNA, hemoglobin, FIB-4, eGFR and hepatitis C. The total runs from 0 to 164, and a higher total goes with higher mortality.
Not a medical device. Not a diagnosis or dosing recommendation.
What is the VACS Index 1.0?
VACS stands for the Veterans Aging Cohort Study. Tate and colleagues published the index in AIDS in 2013 as a mortality index for people who have been on ART for about a year. It adds HIV markers to general markers of blood, liver and kidney health.
Magent's calculator returns the points total and the maximum of 164. This is version 1.0; it isn't the later VACS Index 2.0.
This page explains the arithmetic. It doesn't say what a score means for a particular person.
The VACS Index 1.0 formula
VACS 1.0 = age + CD4 + HIV-1 RNA + hemoglobin + FIB-4 + eGFR + hepatitis C
age < 50 → 0 50–64 → 12 ≥ 65 → 27
CD4 (cells/mm³) ≥ 500 → 0 350–499 → 6 200–349 → 6
100–199 → 10 50–99 → 28 < 50 → 29
HIV-1 RNA < 500 → 0 500–99999 → 7 ≥ 100000 → 14
hemoglobin ≥ 14 → 0 12–13.9 → 10 10–11.9 → 22 < 10 → 38
FIB-4 < 1.45 → 0 1.45–3.25 → 6 > 3.25 → 25
eGFR ≥ 60 → 0 45–59.9 → 6 30–44.9 → 8 < 30 → 26
hepatitis C present → 5
maximum 164Exact expression the calculator uses:
VACS 1.0 = age (<50 0; 50-64 12; ≥65 27) + cd4_cells_mm3 (≥500 0; 350-499 6; 200-349 6; 100-199 10; 50-99 28; <50 29) + hiv_rna_copies_ml (<500 0; 500-99999 7; ≥100000 14) + hemoglobin_g_dl (≥14 0; 12-13.9 10; 10-11.9 22; <10 38) + fib4 (<1.45 0; 1.45-3.25 6; >3.25 25) + egfr_ml_min_1_73m2 (≥60 0; 45-59.9 6; 30-44.9 8; <30 26) + hepatitis_c 5; Tate 2013 VACS Index column (Brown 2014 Table 1 reprint); max 164; caller-assigned FIB-4 and eGFR; not VACS 2.0Inputs
| Input | Meaning | Accepted range |
|---|---|---|
age | Age in years | 18 to 120 |
cd4_cells_mm3 | CD4 count, cells/mm³ | 1 to 2000 |
hiv_rna_copies_ml | HIV-1 RNA, copies/mL | 0 to 10000000 |
hemoglobin_g_dl | Hemoglobin, g/dL | 3 to 22 |
fib4 | FIB-4 index, already calculated | 0.1 to 20 |
egfr_ml_min_1_73m2 | eGFR, mL/min/1.73 m², already calculated | 5 to 200 |
hepatitis_c | Hepatitis C co-infection | yes or no |
How the calculation works
- Find the band for each of the six measured items and take its points.
- Add 5 if hepatitis C co-infection is present.
- Add everything. The total is 0 to 164.
The paper doesn't name low, intermediate or high bands, so the calculator returns the total with no label.
Units
Hemoglobin is in g/dL, CD4 in cells/mm³ and HIV-1 RNA in copies/mL. FIB-4 and eGFR are entered as already-calculated values; the calculator doesn't work them out. A missing value or one outside its range is rejected with an error.
Worked examples
These use Magent's own expected values for the calculator. All three start from CD4 600, HIV-1 RNA 200, FIB-4 1.0, eGFR 90 and no hepatitis C, which all score 0.
Example 1: lowest combination
Age 40, hemoglobin 15 g/dL.
- Age under 50 → 0. Hemoglobin 14 or more → 0.
- Total 0.
Example 2: age 55
Hemoglobin 15 g/dL.
- Age 50–64 → 12. Everything else 0.
- Total 12.
Example 3: hemoglobin 9.0 g/dL
Age 40.
- Hemoglobin under 10 → 38. Everything else 0.
- Total 38.
History of the VACS Index
The calculator cites Tate and colleagues, AIDS, 2013 (volume 27, issue 4, pages 563–572). The abstract describes developing the VACS Index in the Veterans Aging Cohort Study from age, CD4 count, HIV-1 RNA, hemoglobin, liver enzymes, platelets, creatinine and hepatitis C status, with death up to 6 years after starting ART as the outcome. The index was then tested in six independent cohorts of the ART Cohort Collaboration and compared with a restricted index built from age, CD4 count and HIV-1 RNA.
When it's used
The index applies to adults with HIV who have been taking ART for about a year.
Where it's used
The index needs a CD4 count, an HIV-1 RNA result, a hemoglobin, a FIB-4 value, an eGFR and the hepatitis C status, plus age.
Who uses it
The person using the calculator enters the seven values. The calculator finds each band and adds the points.
Limits of the calculation
- The calculator doesn't measure any lab value, and it doesn't work out FIB-4 or eGFR. Race isn't an input.
- It's VACS Index 1.0. It isn't VACS 2.0, which adds albumin, white cell count and BMI.
- The total isn't a risk band or a probability for one person.
- It doesn't establish HIV, liver or kidney disease or anemia, and this page doesn't say what to do with a score.
Clinical decisions belong to a qualified clinician who knows the patient.
How it differs from related calculators
Glossary
- ART: antiretroviral drugs taken for HIV.
- CD4 count: the number of CD4 immune cells per mm³ of blood.
- HIV-1 RNA: viral load, in copies/mL.
- FIB-4: a liver fibrosis index worked out from routine blood tests.
- eGFR: estimated glomerular filtration rate, a measure of kidney function.
Common mistakes
- Using VACS 2.0 inputs. Albumin, white cell count and BMI aren't part of version 1.0.
- Entering hemoglobin in g/L. The calculator expects g/dL.
- Expecting a risk label. The calculator returns the points total alone.
- Scoring CD4 200–349 higher than 350–499. Both bands score 6.
Source
Tate JP, et al. An internationally generalizable risk index for mortality after one year of antiretroviral therapy. AIDS. 2013;27(4):563-572. DOI: 10.1097/QAD.0b013e32835b8c7f. PMID: 23095314
Frequently asked questions
How is the VACS Index 1.0 calculated?
Add the band points for age, CD4, HIV-1 RNA, hemoglobin, FIB-4 and eGFR, plus 5 for hepatitis C. The total is 0 to 164.
Is this the same as VACS Index 2.0?
No. This is version 1.0, without albumin, white cell count or BMI.
Does the VACS Index have risk bands?
No. The paper doesn't name bands, so the calculator returns the total.
Does the calculator work out FIB-4 and eGFR?
No. Enter both as already-calculated values.
What is the highest possible VACS Index 1.0?
164.