NEGATIVE ST PREDICTS ABSENCE OF ASTHMA

A negative skin test (ST) to common aeroallergens was highly correlated with a negative methacholine challenge test result and thus was predictive of the absence of asthma, a recent study by Graif et al has found.

The study had three groups: Group A included 175 patients with active asthma, group B included 100 control patients with no history of asthma, and group C included 150 patients with persistent cough and/or unexplained dyspnea. All patients underwent ST and methacholine challenge.

In groups A, B, and C, respectively, 95%, 54%, and 69% of patients had a positive ST result. In the control group, the probability of patients with asthma having a negative ST result was less than 1.5%.

In group C, the overall sensitivity of ST was 98.2%, and its negative predictive value was 97.8%. Only one of the 46 patients with a negative ST result in this group had a positive methacholine challenge test. Because the test’s specificity for asthma was low (47.4%), however, its positive predictive value was only 51.9%.

The authors noted that methacholine challenge is expensive and time-consuming. Additionally, in patients with allergic rhinitis and smokers with chronic obstructive pulmonary disease, methacholine challenge often resulted in a high false-positive rate.

Although a positive ST result contributed minimally to the diagnosis of asthma, a negative ST result was correlated with a 10- to 20-fold decrease in the probability of an asthma diagnosis.

Graif Y, Yigla M, Tov N, Kramer MR. Value of a negative aeroallergen skin-prick test result in the diagnosis of asthma in young adults: correlative study with methacholine challenge testing. Chest. 2002;122:821-825.

SIDS RISK FACTORS DIFFER DURING DAY AND NIGHT

Data from a large case-control study have pointed to prone sleep position as a risk factor for sudden infant death syndrome (SIDS) during the day. Nighttime deaths were more strongly associated with maternal smoking and social deprivation.

Williams et al analyzed data from the New Zealand Cot Death Study, which enrolled 369 infants who died of SIDS and 1,558 randomly chosen control infants during a three-year period.

Parents of cases and controls were interviewed, and mothers were asked about consumption of alcohol and use of marijuana since giving birth. Infants’ sleeping positions were determined. The maximum and minimum environmental temperatures for both day and night were calculated, as was the amount of clothing and bedding used for the child.

Of the 369 cases, 238 infants had died at night. Maternal smoking and the mother’s being unmarried were more common in infants who died at night, with only 21% having neither risk factor.

The odds ratio for prone sleep position was 3.86 at night and 7.25 during the day. Prone sleep position has long been associated with SIDS occurring at night. According to the authors, the finding that risk was increased with prone sleep during the day was noteworthy.

Williams SM, Mitchell EA, Taylor BJ. Are risk factors for sudden infant death syndrome different at night? Arch Dis Child. 2002;87:274-278.

REGULAR INHALED STEROID USE HELPS AVOID HOSPITALIZATION

In patients with asthma, regular use of low-dose inhaled corticosteroids can prevent asthma-related short- and long-term hospitalization.

Suissa et al used the Saskatchewan Health database to identify and follow 30,569 people who had received at least three prescriptions for asthma medication during any one-year period between September 1975 and December 1991. They assessed the impact of regular corticosteroid use on the risk of hospitalization among the entire cohort of patients; they also evaluated its efficacy in preventing rehospitalization among a subset of patients who were admitted to the hospital at least once.

In the full cohort, regular use of inhaled corticosteroids led to a 31% reduction in the rate of hospital admissions for asthma. In the hospitalized subset, the readmission rate was lowered by 39% with regular use of inhaled corticosteroids. The overall impact of regular inhaled corticosteroid use was calculated as a reduction of 34%. All rates of reduction were stable over time.

The investigators concluded that it was the regularity in use of inhaled corticosteroids that determined their effectiveness. This was important because compliance with inhaled corticosteroids often diminishes with time.

Suissa S, Ernst P, Kezouh A. Regular use of inhaled corticosteroids and the long term prevention of hospitalisation for asthma. Thorax. 2002;57:880-884.

REDUCING CIGARETTE CONSUMPTION AMONG HARD-CORE SMOKERS

A randomized controlled six-month trial conducted by Etter et al found that both nicotine replacement and placebo were equally effective in reducing cigarette consumption among smokers who were not prepared to quit.

Smokers who were not willing to give up smoking but who did agree to try to reduce their daily cigarette consumption by half were randomized to one of three groups. The nicotine group (n = 258) received nicotine replacement in the form of gum, a patch, or an inhaler. The placebo group (n = 261) received equivalent placebo products. The control group (n = 360) received no intervention. Baseline daily cigarette consumption averaged 30 cigarettes in each of the groups.

All groups were mailed follow-up questionnaires at three and six months, asking about the number of cigarettes smoked, level of enjoyment, and reasons for smoking.

After three months, the median reduction in number of cigarettes smoked per day was 10 in the nicotine group, five in the placebo group, and zero in the control group. After six months, the median reductions were 10, 7.5, and 2.5 in the nicotine, placebo, and control groups, respectively.

There was no significant difference between the nicotine and placebo groups in the percentage of participants reducing their cigarette consumption. In fact, in smokers who initially reported smoking more than 30 cigarettes per day, the placebo effect was larger than the treatment effect.

Etter JF, Laszlo E, Zellweger JP, et al. Nicotine replacement to reduce cigarette consumption in smokers who are unwilling to quit: a randomized trial. J Clin Psychopharmacol. 2002;22:487-495.

ASTHMA INTERVENTION COST-EFFECTIVE

Three years ago, the National Cooperative Inner-City Asthma Study (NCICAS) showed that appropriate intervention could improve symptoms and reduce childhood asthma morbidity. In a new analysis, Sullivan et al report that this program was also cost-effective, especially for children with more severe asthma.

NCICAS was a two-year multicenter study conducted in eight US cities. Children with asthma who were ages 5 to 11 were enrolled. One group (518 children) received usual care, and the other (515 children) received specialized counseling from trained social workers. Counseling included encouraging families to get asthma care plans from their physicians, developing the family’s communication skills, and facilitating referrals for community resources.

Counselors worked with both the child and caregiver to identify asthma triggers, improve access to care, and understand the asthma care plan. The intervention began within two months of baseline assessment and lasted for one year.

The number of symptom-free days was an average of 26.6 days greater in the intervention group than in the control group. Yet, the cost of intervention was only $337 per child. In the children with severe asthma, the intervention actually reduced total cost of care.

The authors noted that the success of the NCICAS strategy might have been because it was based on a social-environment model of disease management that involved the child, the caregiver, and the family.

Sullivan SD, Weiss KB, Lynn H, et al. The cost-effectiveness of an inner-city asthma intervention for children. J Allergy Clin Immunol. 2002;110:576-581.

NEW ASSAY FAST AND ACCURATE

A new rapid urine detection assay for Streptococcus pneumoniae has both high sensitivity and specificity, according to a preliminary study by Neuman and Harper.

Two groups of children ranging in age from 3 months to 5 years were enrolled during a one-year period. The study group included 24 children with S pneumoniae bacteremia, and the control group included 72 children with no fever and no apparent bacterial infection. Urine specimens and blood cultures were obtained from all patients. Investigators who were blinded to diagnosis and group performed the assay, and results were interpreted after 15 minutes.

The assay, Binax® NOW, produced a positive result in 23 of 24 patients with pneumococcal bacteremia, which gave it a sensitivity of 95.8%. The result was negative in 67 of 72 control patients, resulting in a specificity of 93%.

The one patient with pneumococcal bacteremia who had a negative result had received antibiotics both orally and intramuscularly for otitis media before the urine specimen was obtained. A repeat blood culture obtained at the same time as the urine specimen was also negative.The authors noted that if additional studies prove its value, the new assay would be a less painful alternative to a complete blood count in children.

Neuman MI, Harper MB. Rapid antigen assay for the diagnosis of pneumococcal bacteremia in children: a preliminary study. Ann Emerg Med. 2002;40:399-404.

RIFAMPIN + PYRAZINAMIDE CAUSES HEPATOTOXICITY

In patients with latent tuberculosis, a two-month regimen of rifampin and pyrazinamide carried a greater risk for grade 3 or 4 hepatotoxicity than did a six-month isoniazid regimen.

Jasmer et al conducted a multicenter trial comparing the two regimens in adults with latent tuberculosis infection. Patients received either 600 mg/d of rifampin plus 20 mg/kg/d of pyrazinamide for two months, or 300 mg/d of isoniazid for six months.

Serum levels of liver enzymes and bilirubin were measured in all patients at one month and also at three months for patients in the isoniazid group. All patients were evaluated for signs and symptoms of adverse events.

Data were available for 411 patients: 207 in the combined therapy group and 204 in the isoniazid group. Hepatotoxicity developed in 54 patients in the combined therapy group and 32 patients in the isoniazid group. Grade 3 or 4 hepatotoxicity occurred in 16 patients in the combined therapy group, compared with two in the isoniazid group.

No patients in either group were hospitalized, and all hepatic abnormalities resolved after discontinuation of treatment. The authors recommended frequent laboratory tests for hepatic injury and toxicity with the combined regimen.

Jasmer RM, Saukkonen JJ, Blumberg HM, et al. Short-course rifampin and pyrazinamide compared with isoniazid for latent tuberculosis infection: a multicenter clinical trial. Ann Intern Med. 2002;137:640-647.

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