Simple, Low-Cost Tests Can Help Diagnose COPD in China, Study Shows

A cross-sectional study published in BMJ Open found accurate and cost-effective screening tests that can identify undiagnosed chronic obstructive pulmonary disease (COPD) in primary care settings in China.

The study also found that combining the Chinese symptom-based questionnaire (C-SBQ) with microspirometry—measuring how much air a patient can breathe out in one forced breath—could provide the most efficient and cost-effective way of identifying patients who need treatment for COPD.

COPD is a common, long-term respiratory condition, and nearly a third of the 3.2 million annual deaths it causes worldwide are in China, making it 1 of the top 3 leading causes of death in the country.

“COPD develops slowly, resulting in delays in symptom recognition and high rates of underdiagnosis,” the study authors wrote, adding that 90% of an estimated 100 million people in China with COPD are undiagnosed. On a global level, 60% to 80% of COPD cases are undiagnosed.

A total of 2445 participants aged 40 and older (mean [SD] age 59.8 [9.6]) were recruited from 1 urban and 1 rural community health center (CHC) in Beijing, Chengdu, Guangzhou, and Shenyang.

Just more than two-thirds of participants (1684) were never smokers and 46.7% had no diagnosed conditions (1142). Hypertension was the most common diagnosed condition with 34.4% (842), only 3.6% (88) had an existing COPD diagnosis, and 8.4% (205) had an existing chronic bronchitis/emphysema diagnosis. Of the 2445 individuals, 39.1% (956) were male.

All participants completed 6 index tests, including 4 screening questionnaires:

• COPD Diagnostic Questionnaire (CDQ) (cut point ≥ 20)
• COPD Assessment in Primary Care to Identify Undiagnosed Respiratory Disease and Exacerbation Risk (CAPTURE) (cut point ≥ 2)
• COPD Screening Questionnaire (COPD-SQ) (cut point ≥ 16)
• C-SBQ (cut point ≥ 17)

The questionnaires were self-reported and were completed immediately after administration of a bronchodilator (400µg, salbutamol). They contained questions about factors such as demographics, smoking status, medical diagnoses, respiratory symptoms, and quality of life.

“Questionnaires were selected to maximize symptom capture and minimize item duplication, while allowing comparison of the most relevant questionnaires,” the authors wrote. “Previously defined cut points were used to identify participants at risk of COPD.”

The 2 other index tests included airflow measurement devices microspirometry and peak flow.

The researchers also conducted a cost-effectiveness analysis. “The strategies were ordered by the number of true cases detected, from least to greatest and the principle of dominance was applied to eliminate redundant strategies (where they were more costly and less effective),” they said. “Each test was then compared with the next best alternative. For the purpose of this paper, the individual index tests and the combination strategy with the highest sensitivity were compared.”

The study found that C-SBQ had the highest sensitivity in detecting airflow obstruction at 63.1% (95% CI, 57.6% to 68.3%) and CDQ had the highest specificity at 78.6% (95% CI, 76.8% to 80.4%).

It also showed that both microspirometry and peak flow devices had higher sensitivity and specificity compared with all 4 questionnaires, with peak flow having the highest sensitivity (67.3%) and microspirometry the highest specificity (89.7%).

“Of the combined screening strategies, C-SBQ combined with airflow measurement devices in parallel (ie, recorded as screen-positive if either test was positive) had the best performance, with sensitivities of 80.5%–81.4% and specificities of 65.5%–68%,” the authors wrote. “Parallel strategies (requiring either test to be positive) optimized sensitivity and serial strategies (requiring both tests to be positive) optimized specificity.”

They also noted that parallel strategies including the C-SBQ had the highest sensitivities, while those including the CDQ had the highest specificity.

The cost-effectiveness analysis of the C-SBQ parallel strategies showed the most expensive strategy was the combination of C-SBQ and microspirometry at £64.20, but it was the most efficient.

“While our analyses used recommended cut-points for the index tests, it is important to explore their optimal cut-points when applied in this context, as many tests were developed with alternate purposes and/or populations in mind,” the authors added. “Thresholds used to indicate airflow obstruction (either in the screening tests or reference test) may not be valid in the whole Chinese population as adequate reference values for lung function are currently unreliable.”

Reference

Pan Z, Dickens AP, Chi C, et al. Accuracy and cost-effectiveness of different screening strategies for identifying undiagnosed COPD among primary care patients (≥40 years) in China: a cross-sectional screening test accuracy study: findings from the Breathe Well group. BMJ Open. Published online September 23, 2021. doi:10.1136/bmjopen-2021-051811