Nitric oxide in Asians misleads asthma tests

Chemical monitoring is a potential method for disease screening

Breath tests provide an important tool in diagnosing asthma and should be covered by health insurers, doctors say.

However, the key chemical marker for asthma, nitric oxide, occurs in the breath of Asian children at nearly twice the level as Caucasian children, which could lead to misdiagnosis, Canadian researchers warn.

Dr. Jeffrey Kam, Straub Clinic & Hospital allergy and asthma specialist, said nitric oxide monitoring is an important procedure and should be covered by medical insurance companies such as the Hawaii Medical Service Association.

HMSA does not cover nitric oxide measurements because they are considered "investigational," or experimental.

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Asian children are at higher risk for being misdiagnosed with asthma or overmedicated for the chronic disease because of higher nitric oxide levels in their breath, according to Canadian researchers.

Compared with Caucasians, nearly twice as much nitric oxide was found in the breath of Asian children in a study of 657 healthy children from ages 9 to 12 in Windsor, Ontario, Canada, researchers reported in the Toronto Globe and Mail. Children of African descent also had high nitric oxide readings.

The study is one of many done in recent years focusing on nitric oxide as a biomarker for asthma. Nitric oxide, a toxic gas, has many roles in the body, including involvement in oxygen transport to the tissues and transmission of nerve impulses.

"Nitric oxide monitoring is one of the things to look for," said Dr. Jeffrey Kam, Straub Clinic & Hospital allergy and asthma specialist. "We're trying to get this technology covered by HMSA and other insurers, but it is considered experimental."

The Hawaii Medical Service Association follows Blue Cross and Blue Shield Association guidelines on coverage for use of nitric oxide to diagnose asthma and other respiratory disorders, said Cliff Cisco, HMSA senior vice president.

The policy is regularly reviewed, but nitric oxide measurements in exhaled breath still are considered "investigational," according to the guidelines.

State Health Department statistics list nearly 33,000 children and about 73,000 adults in Hawaii with asthma.

The disease of the airways is characterized by episodes of breathlessness, wheezing, chest tightness and coughing in early morning or nighttime. It is a leading cause of school absences in Hawaii.

The standard breathing test used to measure how lungs function is done with a device known as a spirometer which measures the volume of air breathed out in the first second of exhalation and gives a reading.

Spirometry involves following directions for a maneuver that younger kids cannot do, Kam said, adding it is also difficult for some adults.

He said a study done at Straub on spirometry results also showed higher levels of nitric oxide in Asian patients. "Looking at Hawaii kids, there are differences in ethnicity," he said, stressing the need to get local data.

"We're trying to talk to HMSA to pay for a study so we could start using this in patients for better asthma control," Kam said. "It's an easier test for us to long-term monitor patients, children especially."

Dr. Elizabeth Tam, chairwoman of the Department of Medicine and respiratory health at the John A. Burns School of Medicine, is doing studies on nitric oxide, mostly with adults.

"All kinds of things seem to affect nitric oxide, including blood pressure medicine commonly used and some things in diet," she said. "So we find it (nitric oxide) helpful as a measure of a person we're following over time ... with response to therapy."

Thomas Kovesi of Children's Hospital of Eastern Ontario, lead investigator of the Canadian study, told the Toronto Globe and Mail, "Traditionally, people have viewed nitric oxide as a black-and-white issue: If your levels are high, you have asthma."

Kam said that if a child is getting regular medications and is not wheezing or coughing but a nitric oxide test shows levels are higher, inflammation is still in the lungs. "This allows us to alter the treatment plan even before they have symptoms," he said.