The Potential of Digital Polymerase Chain Reaction for Improving Diagnostic Yield of Nontuberculous Mycobacteria Pulmonary Disease

Figures & data

Figure 1 Study selection procedure. Patients (n=129) with computed tomography findings suspicious for nontuberculous mycobacteria (NTM) pulmonary disease underwent a bronchoscopic study to collect bronchial lavage fluid samples. Patients with culture positive for Mycobacterium (M) tuberculosis (TB) or NTM subspecies were excluded. The remaining 123 cases were included for further study.

Figure 2 Radiological findings were suspicious for nontuberculous mycobacteria pulmonary disease. (A) Nodular shadow with bronchiectatic changes observed mainly in the middle and lingular bronchopulmonary segments. (B) Bronchiectasis with fibrous cavitary lesions.

Table 1 Patients’ Profile and Positive Partitions During Digital PCR

No of patients	123
Age (median age)	71 (48–90)
Sex
Male	27
Female	96
Symptoms
Cough	39
No symptoms	84
Radiological findings
Nodular or bronchiectatic type	114
Fibrocavitary type	9
Available sample for digital PCR studies per sample
Bronchial lavage fluid
No of samples	123
Range of positive partitions	0–15,640
Sputum
No of samples	76
Range of positive partitions	0–5595
Saliva
No of samples	123
Range of positive partitions	0–6707
Blood
No of samples	123
Range of positive partitions	0
Urine
No of samples	123
Range of positive partitions	0

Table 2 Positive Detection Rate by Digital PCR Test in Patients with Positive or Negative Culture of Nontuberculous Mycobacteria Using Bronchial Lavage Fluid

Sample Type for dPCR	Bronchial Fluid Culture (+) (n = 53)	Bronchial Fluid Culture (-) (n = 70)	All Patients (n = 123)
Bronchial fluid (n = 123)	53 (100%)	16 (22.8%)	69 (56.1%)
Sputa (n = 76)	22 (62.9%)	7 (17.1%)	29 (38.2%)
Saliva (n = 123)	22 (41.5%)	14 (20.0%)	36 (29.3%)
Blood (n = 123)	4 (7.5%)	1 (1.4%)	5 (4.1%)
Urine (n = 123)	2 (3.8%)	4 (5.7%)	6 (4.9%)

Table 3 Positive Predictive Values by Digital PCR

Sample Types	Bronchial Fluid Culture (+)	Bronchial Fluid Culture (-)
Bronchial washing (n = 123)	53	70
No of partitions (+)
0	0 (0.0%)	54 (100.0%)
1	0 (0.0%)	6 (100.0%)
≧ 2	53 (84.1%)	10 (15.9%)
≧ 206	24 (100.0%)	0 (0.0%)
Sputum (n = 76)	35	41
No of partitions (+)
0	13 (27.7%)	34 (72.3%)
1	0 (0.0%)	1 (100.0%)
≧ 2	22 (78.6%)	6 (21.4%)
≧ 206	9 (100.0%)	0 (0.0%)
Saliva (n=123)	53	70
No of partitions (+)
0	31 (27.7%)	56 (64.4%)
1	1 (11.1%)	8 (88.9%)
≧ 2	21 (77.8%)	6 (22.2%)
≧ 64	9 (100.0%)	0 (0.0%)
Sputum + Saliva (n = 123)	53	70
No of partitions (+)
0	23 (29.5%)	65 (70.5%)
1	0 (0.0%)	8 (100.0%)
≧ 2	31 (81.1%)	7 (18.9%)
≧ 114	12 (100.0%)	0 (0.0%)

Table 4 Sensitivity, Specificity, and Predictive Values of Digital PCR Test with Two or More Positive Partitions for Detecting Nontuberculous Mycobacteria

dPCR ≥ 2 (+) Partitions	Sensitivity (%)	Specificity (%)	Positive Predictive Value (%)	Negative Predictive Value (%)
Bronchial lavage fluid	100 (53/53)	85.7 (60/70)	84.1 (53/63)	100 (60/60)
Sputum	62.9 (22/35)	85.4 (35/41)	78.6 (22/28)	72.9 (35/48)
Saliva	39.6 (21/53)	91.4 (64/70)	77.8 (21/27)	66.7 (64/96)
Sputum and saliva	56.6 (30/53)	90.0 (63/70)	81.1 (30/37)	73.3 (63/86)

Table 5 Relationship Between Bronchial Fluid Culture Positivity and Number of Positive Partitions in the dPCR Test

Time of Culture (+) for Nontuberculous Mycobacteria Using Bronchial Lavage Fluid	dPCR-Positive Partitions Using Bronchial Lavage Fluid (Median, Range)	dPCR-Positive Partitions Using Saliva (Median, Range)
Fourth week	269 (7–15,640)*	85 (7–15,640)*
Eighth week	73 (2–12,833)	0 (0–286)

Note: *p<0.05 vs culture (+) at 8th week.