ACE INHIBITORS REDUCE RISK OF PNEUMONIA IN ASIAN PATIENTS

The available literature has suggested that angiotensin-converting enzyme (ACE) inhibitors may confer protection against pneumonia in elderly patients. In a recent study, Ohkubo et al confirmed that ACE inhibitor use reduces the risk of pneumonia in Asian patients, but the researchers were unable to make any clinical recommendations from these findings.

PROGRESS (the Perindopril Protection Against Recurrent Stroke Study) randomized 6,105 patients with a history of stroke from 172 centers in 10 countries. After completing a four- to six-week run-in period during which they took 2 to 4 mg of perindopril daily, patients either continued receiving perindopril at 4 mg/d or were given an identical placebo. They were evaluated five times during the first year and every six months thereafter. At each visit, patients reported the occurrence of major health-related events, including pneumonia. The cause of death was reviewed for all patients who died during the study. In addition, blood samples were obtained, and genotyping of the ACE insertion/deletion (ACE I/D) polymorphism was done using polymerase chain reaction.

Thirty-nine percent of the patients were Asian, and 61% were non-Asian. The median length of follow-up was 3.9 years. Pneumonia occurred in 3.8% of the treatment group and 4.7% of the placebo group. There was a significant reduction of risk in the subgroup of treated patients who were of Asian ethnicity (the relative risk reduction was 47%), but no significant reduction in risk was seen in the non-Asian patients.

Some of the ACE polymorphisms were more common in the Asian patients than in the other subgroups. However, ACE I/D polymorphisms did not appear to affect either patients’ risk of pneumonia or their likelihood of deriving protection against pneumonia from perindopril.

The authors concluded that ACE inhibitors might protect against pneumonia in some patients, but there was no conclusive evidence that they should be considered a therapeutic option.

Ohkubo T, Chapman N, Neal B, et al. Effects of an angiotensin-converting enzyme inhibitor–based regimen on pneumonia risk. Am J Respir Crit Care Med. 2004;169:1041-1045.

ENVIRONMENTAL PEANUT ALLERGEN LEVELS LOWER THAN EXPECTED

Because of its severity, peanut allergy frequently causes patients and their families to limit their activities to avoid exposure to peanuts. However, a study by Perry et al suggests that many of these limitations are not necessary: The researchers were unable to detect levels of airborne allergen in environments simulating public eating places, airplanes, and sporting events—places where peanuts are usually present. Furthermore, they found that most surfaces contaminated with peanut allergen can be cleaned relatively easily.

Nineteen adult volunteers without peanut allergy consumed various types of peanut products in a manner designed to simulate common situations. For example, they ate peanut butter sandwiches to simulate a school cafeteria, and they shelled and ate roasted peanuts (and were asked to walk on the shells) to simulate a sports arena. Air samples were collected from the areas immediately around the volunteers and from sites up to 10 feet away. The volunteers also cleaned smeared peanut butter off their hands using different cleaners.

Additionally, table surfaces had been tested after peanut butter was wiped off using various cleaners. Furthermore, peanut allergen (Ara h 1) levels were measured on tables and surfaces at six participating schools.

Most cleaners effectively removed all traces of Ara h 1 from tabletops and hands. During the simulations, levels of airborne allergen were not detectable—even though peanut exposure far exceeded that which would normally be encountered. Perry et al acknowledge the possibility that during the simulations some airborne peanut allergen may have been present, but it was below the detection threshold of the assay used.

In the six schools tested, no food preparation areas or desktops had detectable levels of Ara h 1. However, Ara h 1 was found on one of 13 water fountains tested, at a level of 130 ng/mL.

The authors noted that ideally a similar study should be performed challenging patients with peanut allergy in these simulated settings. Nevertheless, they found that the risk of exposure to peanut allergen is relatively low in the environment if surfaces and hands are cleaned properly.

Perry TT, Conover-Walker MK, Pomés A, et al. Distribution of peanut allergen in the environment. J Allergy Clin Immunol. 2004;113:973-976.

IMMUNOTHERAPY USING HOUSE DUST MITE ALLERGEN CONFERS SLIGHT BENEFIT

House dust mite is a common indoor allergen and asthma trigger. Recently, Maestrelli et al conducted a randomized, double-blind, placebo-controlled trial to determine if house dust mite–specific immunotherapy affected asthma medication use and lung function. Their findings showed that immunotherapy had a marginally significant effect that could be attributed to a decrease in the allergic response.

The study included 72 patients with a history of asthma and sensitization to house dust mite. Patients were observed for one year before the study; they were then randomized to receive either immunotherapy or placebo. In addition, they were given instructions on allergen avoidance, along with allergen-impermeable mattress and pillow covers.

An extract containing both Dermatophagoides pteronyssinus (Der p 1) and Dermatophagoides farinae (Der f 1) allergens was used for immunotherapy. Clinical assessments were performed at baseline and then every three months for three years. Patients also underwent skin tests at baseline and yearly thereafter.

The levels of house dust mite allergen in patients’ homes did not change during the study. Immunotherapy was associated with significantly less skin sensitivity to the allergen, whereas in the placebo recipients there was a trend toward increasing skin sensitivity.

PEF values improved significantly in the immunotherapy group but remained unchanged in the placebo recipients. During the third year of treatment, patients’ use of bronchodilators in autumn decreased significantly in the treatment group. The improvement in PEF was similar to that seen in a study using low-dose budesonide.

The authors observed that immunotherapy with house dust mite allergen provided small but significant benefits when used with traditional asthma care. They cautioned that immunotherapy should not be used in patients with severe asthma because of safety risks.

Maestrelli P, Zanolla L, Pozzan M, Fabbri LM. Effect of specific immunotherapy added to pharmacologic treatment and allergen avoidance in asthmatic patients allergic to house dust mite. J Allergy Clin Immunol. 2004;113:643-649.

PNEUMOCOCCAL VACCINE NARROWS RACIAL DISPARITY IN DISEASE INCIDENCE

African-Americans have historically had a higher incidence of invasive pneumococcal disease than do white Americans. The widest disparities have occurred among two groups: children younger than 2 and adults. A study by Flannery et al evaluated the effects of the pneumococcal conjugate vaccine on disease prevalence for young children. They found that use of the childhood pneumococcal vaccine has reduced the racial disparity in disease incidence.

CDC data were used to calculate incidence rates for 1998 through 2002. Vaccine coverage rates in children between ages 19 and 35 months were calculated for 2001 (n = 3,576) and 2002 (n = 3,597) using data from the National Immunization Survey.

Incidence rates for pneumococcal disease dropped in all populations after the vaccine was introduced. The differences in incidence between white and African-American children decreased by 60%, from 35.9 cases per 100,000 in the prevaccine period to 14.4 per 100,000 in 2002.

By 2002, the incidence of pneumococcal disease caused by the seven vaccine serotypes had decreased by 87% in white children and by 92% in African-American children. The use of the pneumococcal conjugate vaccine contributed to the decrease in disease risk among black children.

Flannery B, Schrag S, Bennett NM, et al. Impact of childhood vaccination on racial disparities in invasive Streptococcus pneumoniae infections. JAMA. 2004;291:2197-2203.

ICU ADMISSIONS UP, OUTCOMES BETTER IN HIV PATIENTS

Although the use of highly active antiretroviral therapy (HAART) in HIV-infected patients has drastically reduced the number of hospital admissions for HIV-associated disorders, HAART’s effect on ICU admissions has not been assessed. To investigate this issue, Narasimhan et al compared the characteristics of HIV-infected patients admitted to the ICU of a large urban hospital during two separate periods: the first six months of 2001 and the year between November 1991 and October 1992. The researchers found that ICU admissions were more frequent in 2001 than in the earlier period, but non–HIV-related conditions were usually the cause.

During the first six months of 2001, 53 HIV-infected patients had a total of 63 ICU admissions. During the year ending in October 1992, 65 HIV-infected patients were admitted to the ICU. Patients in 2001 were more likely to have acquired HIV from injection drug use. Twenty-eight patients in 2001 were receiving HAART; in comparison, only 22 patients had been given any type of antiretroviral therapy in 1991-1992.

In both time periods studied, the most common reason for ICU admission among HIV-infected patients was respiratory failure, but the frequency was lower in 2001 than in 1991-1992 (22% vs 54%, respectively). Two thirds of the ICU admissions in 2001—but only 12% of ICU admissions in the earlier period—were for reasons unrelated to HIV infection.

Survival to hospital discharge was significantly higher in 2001 than in 1991-1992 (71% vs 49%, respectively). Serum albumin level was the only laboratory measurement inversely correlated with survival in 2001.

Contrary to what the investigators had originally hypothesized, post-HAART patients had increased ICU admissions, knew that they were seropositive, and had very different types of health disorders and outcomes than did patients treated before the widespread use of HAART.

Narasimhan M, Posner AJ, DePalo VA, et al. Intensive care in patients with HIV infection in the era of highly active antiretroviral therapy. Chest. 2004;125:1800-1804.

M PNEUMONIAE INFECTION CAN TRIGGER ASTHMA IN CHILDREN

Recent research has suggested a possible role for Mycoplasma pneumoniae in the pathogenesis of asthma. A prospective study by Biscardi et al tested children who visited the emergency department with asthma for acute infections with M pneumoniae or Chlamydia pneumoniae. They found that in children who are predisposed to develop asthma, M pneumoniae infection may trigger its onset.

All children ages 2 to 15 years who were hospitalized for severe acute asthma at one institution between January 1999 and June 2001 were included in the study. Nasopharyngeal samples were taken to test for various respiratory pathogens using polymerase chain reaction. Blood samples were used to test for immunoglobulin (Ig) G and IgM specific for M pneumoniae and C pneumoniae. Two to four weeks later, blood samples were again taken, and all of the tests were repeated.

Patients were divided into two groups according to their asthma history. Group 1 included patients with known asthma; group 2 included children whose initial emergency department visit had been for their first asthma attack. Allergic children who were examined as outpatients served as the controls.

Group 1 included 119 children. M pneumoniae was detected in 24 children (20%), and four had C pneumoniae infection. Chest radiographs revealed pneumonia in 17 children, four of whom had M pneumoniae infection.

There were 51 children in group 2. Twenty-six (50%) were diagnosed with M pneumoniae infection—22 children had positive IgM in their initial serum sample and four in their second sample. C pneumoniae infection was detected in three children. Chest radiography indicated pneumonia in eight children, five of whom tested positive for M pneumoniae. Fifty-two percent of group 2 children had a family history of asthma or atopy, 27% had a history of atopic dermatitis, and 51% had elevated serum IgE levels.

Only eight (5%) of the 152 controls had evidence of M pneumoniae infection. Testing for C pneumoniae was performed in 120 of the controls; results were positive in three cases.

During the year after hospitalization, asthma recurred in 15 of the 26 group 2 patients diagnosed with M pneumoniae, and in all three who had C pneumoniae infections. Four patients in group 2 did not initially receive macrolide treatment. All four had a severe asthma attack within three weeks of initial hospitalization, and two of these required intensive care. None of the children in the control group had any recurrence of asthma or allergy symptoms resulting in admission to the hospital or emergency department.

Biscardi et al suggest that about one half of first severe asthma attacks in children can occur during an infection with M pneumoniae. In addition, in children with M pneumoniae who are having their first asthma attacks, failure to give macrolides greatly increases the risk of a subsequent severe attack requiring hospitalization or admission to the ICU.

Biscardi S, Lorrot M, Marc E, et al. Mycoplasma pneumoniae and asthma in children. Clin Infect Dis. 2004;38:1341-1346.