Early diagnosis of HIV-1 infection in infants in Dar es Salaam, Tanzania

OBJECTIVES

To evaluate two simple methods, an immune complex dissociation (ICD) p24 antigen assay and an HIV-1-specific IgA antibody assay, for the early demonstration of HIV-1 infection in infants, using the polymerase chain reaction (PCR) as the reference method.

DESIGN AND SETTING

Group A: 143 HIV-1-seropositive and 134 -seronegative mothers and their infants were recruited at delivery at the main hospital in Dar es Salaam, Tanzania. Group B: 26 HIV-PCR-positive hospitalized children in Dar es Salaam, 3-15 months old and suspected of having an HIV-related illness.

METHODS

Blood samples were taken from mothers and infants in group A at intervals during the children's first 24 months and once from each of the children in group B. Peripheral blood mononuclear cells were tested by nested PCR for viral DNA. Plasma samples were tested by the Coulter p24 antigen (ag) enzyme-linked immunosorbent assay (ELISA) after acid dissociation of p24 antigen-antibody complexes. All p24-ag-positive reactions were confirmed by neutralization. Viral specific IgA antibodies were demonstrated in plasma by a modified ELISA.

RESULTS

One hundred and sixty-three of 174 samples from seropositive mothers were PCR-positive (sensitivity 93.7%) and 612 of 614 samples from seronegative mothers and children of seronegative mothers were PCR-negative (specificity 99.7%). Twenty-nine of 145 (20.0%) children born to seropositive mothers were positive by PCR when tested during the first year of life. By use of both the p24 ag ELISA and the IgA antibody ELISA in combination, HIV-1 infection was detected in 9 of 17 (53%) PCR-positive children 1-8 weeks old, in 15 of 18 (83%) PCR-positive children 9-26 weeks old and in 23 of 24 (96%) PCR-positive children 27-52 weeks old. The specificities of the p24 ag ELISA and the IgA ELISA were 100%.

CONCLUSIONS

The p24 ag assay and the IgA antibody ELISA, when used in combination, had a high sensitivity and specificity for detection of HIV-1 infection in infants, especially in those above the age of 6 months.

Hypoxaemia in children with severe pneumonia in Papua New Guinea

OBJECTIVES

To investigate the severity and duration of hypoxaemia in 703 children with severe or very severe pneumonia presenting to Goroka Hospital in the Papua New Guinea highlands; to study the predictive value of clinical signs for the severity of hypoxaemia, the predictive value of transcutaneous oxygen saturation (SpO2) and other variables for mortality.

DESIGN

Prospective evaluation of children with severe or very severe pneumonia. SpO2 was measured at the time of presentation and every day until hypoxaemia resolved. Children with a SpO2 less than 85% received supplemental oxygen. By comparing with a retrospective control group for whom oxygen administration was guided by clinical signs, we evaluated whether there was a survival advantage from using a protocol for the administration of oxygen based on pulse oximetry. We determined normal values for oxygen saturation in children living in the highlands.

RESULTS

In 151 well, normal highland children, the mean SpO2 was 95.7% (SD 2.7%). The median SpO2 among children with severe or very severe pneumonia was 70% (56-77); 376 (53.5%) had moderate hypoxaemia (SpO2 70-84%); 202 (28.7%) had severe hypoxaemia (SpO2 50-69%); and 125 (17.8%) had very severe hypoxaemia (SpO2 < 50%). Longer duration of cough or the presence of hepatomegaly or cyanosis predicted more severe degrees of hypoxaemia. After 10, 20 and 30 days from the beginning of treatment, respectively 102 (14.5%), 38 (5.4%) and 19 (2.7%) of children had persistent hypoxaemia; 46 children (6.5%) died. Predictors of death were low SpO2 on presentation, severe malnutrition, measles and history of cough for more than 7 days. The mortality risk ratio between the 703 children managed whose oxygen administration was guided by the use of pulse oximetry and the retrospective control group who received supplemental oxygen based on clinical signs was 0.65 (95%CI 0.41-1.02, two-sided Fisher's exact test, P = 0.07).

CONCLUSION

There is a need to increase the availability of supplemental oxygen in smaller health facilities in developing countries, and to train health workers to recognise the clinical signs and risk factors for hypoxaemia. In moderate sized hospitals a protocol for the administration of oxygen based on pulse oximetry may improve survival.