Prevalence and determinants of rheumatic heart disease among school-going children in Dhanusha district, southern Nepal: a cross-sectional echocardiographic screening study

This cross-sectional echocardiographic study of 4,536 school children in Dhanusha, Nepal, reveals the country's highest documented rheumatic heart disease prevalence (18.7 per 1,000), with two-thirds of cases being subclinical and female sex identified as the sole independent predictor, highlighting the critical need for school-targeted screening programs.

The Gist

Imagine a silent thief that steals the health of children, leaving no loud alarms until it's too late. This thief is Rheumatic Heart Disease (RHD). It starts with a common sore throat, but in some children, their immune system gets confused and attacks their own heart valves instead of the bacteria. Over time, this damages the heart, often without the child ever feeling sick.

For years, doctors in Nepal tried to catch this thief by listening to children's hearts with a stethoscope. But it's like trying to find a whisper in a hurricane; the stethoscope misses most of the cases because the damage is happening "under the hood" before any noise is made.

This study decided to use a high-tech flashlight called an echocardiogram (an ultrasound of the heart) to look inside the hearts of 4,536 school children in the Dhanusha district of Nepal. Here is what they found, explained simply:

1. The Hidden Epidemic

The researchers found that RHD is much more common than anyone thought in this area.

• The Numbers: About 19 out of every 1,000 children had the disease. This is the highest rate ever recorded in Nepal.
• The "Silent" Majority: The most shocking discovery is that two-thirds (64.7%) of these children had no symptoms at all. Their hearts were damaged, but they had no heart murmur (the "noise" doctors listen for) and felt perfectly fine. If they had only used stethoscopes, they would have missed nearly 65% of the sick children.

2. Who is Most at Risk?

The study acted like a detective looking for patterns:

• Girls vs. Boys: The disease was significantly more common in girls. If you imagine the risk as a scale, girls were about 60% more likely to have the disease than boys.
• The "Sweet Spot" Age: The danger zone for girls was between 10 and 14 years old. This is when the prevalence peaked.
• The School Factor: The study found that which school a child attended mattered almost as much as their gender. Some schools had much higher rates of disease than others. This suggests that the environment of the school (perhaps how crowded the classrooms are or how easily germs spread there) plays a huge role in who gets sick.

3. The "Heart Valve" Damage

When they looked at the damaged hearts, they saw a clear pattern:

• The mitral valve (a door in the heart that controls blood flow) was the main victim. It was damaged in almost 90% of the cases.
• The damage was usually in the early stages, meaning it was caught before the heart was completely destroyed. This is good news because early treatment can stop the damage from getting worse.

4. Why Stethoscopes Failed

The study compared the "old way" (listening with a stethoscope) to the "new way" (ultrasound).

• The stethoscope only caught 35% of the cases.
• The ultrasound caught 100% of the cases.
• The Analogy: Using a stethoscope to find RHD is like trying to find a leak in a boat by looking at the water outside; you might see a few drops, but you'll miss the big hole underwater. The ultrasound is like diving in to see the whole boat.

5. What This Means for the Future (According to the Paper)

The authors suggest that to stop this silent thief, we need to change the strategy:

• Stop guessing, start scanning: Because the disease is so hidden, listening to hearts isn't enough. We need to use portable ultrasound machines in schools.
• Target the schools: Since the disease clusters in specific schools, it makes sense to screen entire schools rather than just picking random children.
• Focus on girls: Since girls are at higher risk, screening programs should pay special attention to them, especially those aged 10–14.
• Start early: Because the disease was found even in the youngest children (6–9 years), screening shouldn't wait until kids are teenagers; it should start when they first enter school.

In a nutshell: This paper reveals that in Dhanusha, Nepal, a silent heart disease is affecting far more children than we realized, especially girls, and it is hiding so well that our old tools (stethoscopes) can't find it. To protect these children, we need to use better tools (ultrasound) and look at the whole school environment, not just the individual child.

Technical Summary

Technical Summary: Prevalence and Determinants of Rheumatic Heart Disease in Dhanusha, Nepal

Problem Statement
Rheumatic heart disease (RHD) remains a leading preventable cause of cardiac death among children in low- and middle-income countries (LMICs). While Nepal has acknowledged RHD as a public health issue for decades, reliable epidemiological data has been scarce. Previous studies in Nepal relied heavily on cardiac auscultation, a method known to miss subclinical disease, which is estimated to be five to eight times more prevalent than clinically manifest disease. Furthermore, no echocardiographic screening study had been conducted in the Dhanusha district, a densely populated, low-income region in southern Nepal characterized by agricultural dependence and limited access to specialist healthcare. Existing data from other Nepalese districts suggested a prevalence of 10.2 per 1,000, but the burden in the Terai region remained unknown. Additionally, no prior study in Nepal had quantified the intraclass correlation coefficient (ICC) for school-level clustering, a critical parameter for designing future cluster-based surveillance studies.

Methodology
The authors conducted a cross-sectional, school-based echocardiographic screening study in Dhanusha district between January 2023 and December 2024.

• Study Population: The study targeted children aged 6–16 years enrolled in public schools (grades pre-primary through 10). Private schools were excluded to focus on the most socioeconomically vulnerable populations.
• Sampling Strategy: A four-stage cluster sampling approach was employed. Municipalities were selected based on geographic and socioeconomic strata, followed by the selection of one ward and one large public school per ward. All eligible children present on screening days were invited.
• Sample Size: The study enrolled 4,536 children from eight public schools, exceeding the calculated minimum requirement of 4,105 to account for a design effect (DEFF) of 1.5 and anticipated non-attendance.
• Diagnostic Protocol:
  • Auscultation: Performed by a cardiologist using a stethoscope.
  • Echocardiography: All participants underwent comprehensive transthoracic echocardiography using a portable ultrasound machine (Sonosite M-Turbo). Standard views (PLAX, PSAX, AP4Ch, AP5Ch) with 2D and color Doppler assessment were obtained.
  • Classification: RHD was classified using the 2012 World Heart Federation (WHF) criteria. Cases were categorized as "borderline" or "definite." Subclinical RHD was defined as echocardiographic findings without an audible murmur.
  • Quality Control: Suspicious findings were reviewed by a second senior cardiologist, with final diagnoses reached by consensus.
• Statistical Analysis: Prevalence was calculated with exact binomial 95% confidence intervals. Independent predictors were identified using random-effects logistic regression with school as a random intercept to account for clustering. The ICC was estimated to quantify school-level variance.

Key Results

• Prevalence: The overall prevalence of borderline or definite RHD was 18.7 per 1,000 (95% CI 15.1–23.0). This breaks down to 6.8 per 1,000 for definite RHD and 11.9 per 1,000 for borderline RHD. This is the highest documented echocardiographic prevalence in Nepal to date, significantly higher than the 10.2 per 1,000 reported in a previous study in Sunsari district.
• Subclinical Disease: Subclinical RHD accounted for 64.7% of all cases. The sensitivity of cardiac auscultation for detecting any RHD was only 35.3%.
• Demographic Associations:
  • Sex: Prevalence was significantly higher in girls (23.3 per 1,000) compared to boys (13.6 per 1,000; P=0.02).
  • Age: Among girls, the peak prevalence occurred in the 10–14 year age group (26.0 per 1,000). In boys, prevalence was highest in the 6–9 year group (14.8 per 1,000) and rose again in the 15–16 year group.
  • Predictors: In multivariable random-effects logistic regression, female sex was the sole independent individual-level predictor of RHD (OR 1.60; 95% CI 1.02–2.53; P=0.043). Age was not a significant predictor in the adjusted model.
• Valve Involvement: Mitral valve involvement predominated (41.2% isolated mitral, 89.4% total mitral involvement). Aortic involvement was less common (10.6%).
• Clustering: The study identified significant school-level clustering with an ICC of 0.19 (95% CI 0.07–0.44). This implies that the school a child attends explains approximately 19% of the variance in RHD risk, a magnitude comparable to the effect of biological sex. The resulting design effect was approximately 109.
• Symptoms: No individual RHD-related symptom (throat pain, joint pain, chorea) reported in the past 12 months was significantly associated with echocardiographic RHD status. Notably, children with no reported symptoms had a higher prevalence of RHD (2.4%) than those with at least one symptom (1.5%).

Significance and Claims
The paper claims that this study provides the first echocardiographic evidence of RHD burden in the Dhanusha district, revealing a prevalence that places the region among the high-endemic zones globally. The authors highlight several critical implications:

1. Limitations of Auscultation: The finding that nearly two-thirds of cases are subclinical reinforces that auscultation-based surveillance is insufficient for RHD control in high-burden settings.
2. Targeted Screening: The identification of female sex as a primary risk factor and the peak prevalence in girls aged 10–14 suggests that screening and secondary prophylaxis programs should prioritize this demographic.
3. School-Level Determinants: The high ICC (0.19) indicates that structural factors at the school level (e.g., crowding, ventilation, access to antibiotics) are major independent determinants of RHD risk. This supports a shift from individual-based screening to school-targeted strategies, which may be more cost-effective.
4. Study Design Implications: The authors emphasize that the high design effect (≈109) necessitates a larger number of clusters (schools) in future surveillance studies to ensure adequate statistical power. They recommend that future studies in the Terai region enroll at least 20–25 schools.
5. Early Intervention: The high prevalence in the youngest age groups (6–9 years) suggests that screening should begin at school entry (age 6) rather than waiting for older children, contrasting with strategies in lower-prevalence regions.

The study concludes that integrating portable echocardiography into routine school health programs in Dhanusha and similar districts is urgent, with a specific focus on girls and high-risk schools, to prevent progression to severe valvular damage.