Description

Kebebew et al developed the CaPTHUS (calcium, parathyroid hormone, ultrasound) model for evaluating a patient with primary hyperparathyroidism. This can help determine if the disorder is due to involvement of one or more than one parathyroid glands. The authors are from the University of California in San Francisco.


 

Parameters:

(1) total serum calcium

(2) serum intact parathyroid hormone (PTH) concentration

(3) sestamibi scan

(4) neck ultrasound

(5) concordance in the findings from the sestamibi and ultrasound scans

Parameter

Findings

Points

total serum calcium

< 3 mmol/L

0

 

>= 3 mmol/L (>= 12 mg/dL)

1

serum intact PTH

< 2 times upper limit of normal

0

 

>= 2 times the upper limit of normal

1

sestamibi scan

does not show 1 enlarged gland

0

 

shows 1 enlarged gland

1

neck ultrasound

does not show 1 enlarged gland

0

 

shows 1 enlarged gland

1

concordance of two scans

not concordant

0

 

concordant (both show a single enlarged gland on the same side of the neck)

1

 

where:

• The sestamibi scan can show 0, 1 or multiple enlarged glands. No glands and multiple glands would be scored 0. Ditto for the ultrasound scan.

• I would think that the presence of multiple glands on sestamibi scan and/or ultrasound scan would make me think of multi-gland disease.

 

total score =

= SUM(points for all 5 parameters)

 

Interpretation:

• minimum score: 0

• maximum score: 5

• A patient with a score >= 3 can have minimally invasive surgery to remove the single implicated parathyroid gland. The patient does not require intra-operative PTH assay or additional imaging studies.

• A patient with a score < 3 should have additional testing to exclude multi-gland disease.

 

Performance:

• A score >= 3 was 100% specific but only 44% sensitivity for single gland disease.

• A score >= 2 had the maximum Youden score (specificity 89%, sensitivity 60%).

• A score >= 1 was the most sensitive (89%) but the lowest specificity (59%).

 


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