Body mass index (BMI) at the time of HIV diagnosis can predict survival according to a study conducted in The Gambia and published in the October 1st edition of the Journal of Acquired Immune Deficiency Syndromes. The study found that patients with a BMI below 16 have a similar prognosis to those with CD4 cell counts below 200 cells/mm3. The investigators believe that BMI could be a low cost, low technology means of assessing when an individual needs to start antiretroviral therapy.
Although viral load measurements and CD4 cell counts are basic diagnostic tools and play a key role in the initiation and monitoring of highly active antiretroviral therapy (HAART) in rich countries, many resource-limited countries lack the funds or technology to use these tests. Investigators from the London School of Hygiene and Tropical Medicine wished to see if BMI at the time of initial HIV diagnosis provided a robust, affordable, and easily used monitoring tool, capable of determining the prognosis of HIV-positive individuals.
Between 1992 and 2001 a total of 1657 individuals in The Gambia had their BMI assessed within three months of their initial HIV diagnosis. CD4 cell count was also measured and patients had their Karnofsky score assessed. The Karnofsky score is a measure of how well a patient is doing, on a scale from 0 to 100, where 100 is when the patient has no complaints or evidence of disease, 50 is when the patient requires considerable assistance and frequent medical care, and 0 is when the patient is dead.
At the time of HIV diagnosis, individuals had a median BMI of 18.8 kg/m2, the median CD4 cell count was 250 cells/mm3 and the median Karnofsky score was 80. A total of 11% of patients were assessed as having wasting at baseline, and at this point 16% were also diagnosed with tuberculosis.
Investigators found a significant relationship between CD4 cell count and BMI at baseline. The median BMI for patients with a CD4 cell count below 200 cells/mm3 was 17.9 kg/m2. Patients with a CD4 cell count between 200 – 500 cells/mm3 had a BMI of 19.5 kg/m2 and individuals with a CD4 cell count above 500 cells/mm3 had a BMI above 20 kg/m2 (p
Karnofsky score was also significantly related to BMI (p = 0.05).
BMI at the time of HIV diagnosis was able to predict survival time. A total of 849 patients (51%) died during follow-up with individuals with a low BMI at diagnosis having the greatest risk of death. The overall mortality rate was 229 per 1000 patient years of follow-up and median survival was 2.8 years. However, median survival for patients with a BMI below 16 was only 0.8 years compared to 8.9 years for individuals with a BMI above 22 at baseline (p
Patients with a BMI below 18 at diagnosis were 3.4 times more likely to die than individuals with a BMI above 18 kg/m2, i.e. the hazard ratio (HR) was 3.4. The HR of death for individuals with a BMI below 16 was 6.4 compared to patients with a BMI above 22 kg/m2. The investigators note that this “is similar to the HR of those with a CD4 cell count below 200 cells/mm3 compared with those with a CD4 cell count above 500 cells/mm3 (HR 6.8).”
Even after adjusting for type of HIV (HIV-1, HIV-2 and dual infection), CD4 cell count at baseline, age, sex, infection with tuberculosis, and the receipt of Pneumocystis pneumonia (PCP) prophylaxis, a BMI below 16 kg/m2 still involved a HR of death of 2.5.
Even if a patient had a high BMI at baseline, they still had a significantly increased risk of death if it fell during follow-up. A total of 166 patients had a BMI above 18 kg/m2 at diagnosis. Of these 109 died during follow-up. Median survival for these patients, once their BMI dropped below 18 kg/m2, was 0.8 years, and their mortality rate was 571 per 1000 patient-years. This compared to a mortality rate of 112 per 1000 patient years for patients whose BMI remained above 18 kg/m2.
“Our data show that baseline BMI recorded within three months of the diagnosis of HIV infection is a strong and independent predictor of mortality in this West African cohort. The magnitude of this predictive effect, and the sensitivity and specificity were similar to those of the CD4 cell count on mortality”, write the investigators. They add that they found a persistent and strong “independent association between BMI and mortality; indeed the increased risk of a BMI
The investigators believe that their findings have important implications for antiretroviral access programmes in resource limited countries, and conclude “BMI at diagnosis is a low-technology, affordable, prognostic indicator, independent of age, sex, CD4 cell count, or HIV type.”
van der Sande MAB et al. Body mass index at the time of HIV diagnosis: a strong and independent predictor of survival. J Acquir Immune Defic Syndr 37: 1288–1294, 2004.