Methods
All of the children's parents were given a survey to establish demographic data and judge exposure. The investigators questioned parents on the brand and amount of formula ingested and matched it up to government data on the amount of melamine in each brand. Children were then put through varying degrees of biochemical and ultrasound testing.
All the children were under 36 months of age, the population most at risk of melamine stones.
The primary outcome was the presence of kidney stones.
The General Administration of Quality Supervision and Quarnatine of the PRC analyzed 22 brands of formula and reported the amount of melamine. The researchers then categorized each formula as:
- High melamine (over 500 ppm)
- Moderate melamine (less than 150 pm)
- No-melamine.
Ultrasounds were reported as:
- Definite stones
- Suspected stones (increased sporadic, punctiform echogenicity in the kidneys or pyelocalyceal system)
- No stones
Result
The all important table 1.
In 589 exams they found definite 50 stones, 112 suspected stones and 427 children were stone free.
In 589 exams they found definite 50 stones, 112 suspected stones and 427 children were stone free.Most of the children with stones did not oliguria, dysuria or edema. Only two of 34 stone formers (6%) had hematuria and only 1 had leukoturia (3%). None of the children with suspected stones had hematuria and only one had leukocyturia (1.3%).
Microalbuminuria was found in more of the children with stones (10%) or suspected of having stones (13.6%) compared to the stone free children (5.6%). Symptoms were not helpful in distinguishing stone formers from the stone free.
Fifty-six children had serum creatinine checked (22 with stones, 21 with suspected stones and 13 without). All of the creatinines were normal.
Interestingly 62 of 404 children had a calcium to creatinine ratio that exceeded age based targets. The 15% rate of hypercalciuria was not associated with stone risk in this study (p=0.34).
In multivariate analysis exposure to high-melamine milk (7x as likely) and pre-term birth (4.5x as likely) were significantly associated with stone formation.
The primary conclusion is that the physical and biochemical lab add nothiong to the evaluation of melamine stones. The birth history and the melamine exposure assessment are critical but need to be followed up by an ultra-sound.
The authors note that only 23 of 121 children exposed to high-melamine formula developed stones
Microalbuminuria was found in more of the children with stones (10%) or suspected of having stones (13.6%) compared to the stone free children (5.6%). Symptoms were not helpful in distinguishing stone formers from the stone free.
Fifty-six children had serum creatinine checked (22 with stones, 21 with suspected stones and 13 without). All of the creatinines were normal.
Interestingly 62 of 404 children had a calcium to creatinine ratio that exceeded age based targets. The 15% rate of hypercalciuria was not associated with stone risk in this study (p=0.34).
In multivariate analysis exposure to high-melamine milk (7x as likely) and pre-term birth (4.5x as likely) were significantly associated with stone formation.
The primary conclusion is that the physical and biochemical lab add nothiong to the evaluation of melamine stones. The birth history and the melamine exposure assessment are critical but need to be followed up by an ultra-sound.The authors note that only 23 of 121 children exposed to high-melamine formula developed stones
