Performance of alpha-defensin lateral flow test after synovial fluid centrifugation for diagnosis of periprosthetic knee infection

Table 1 Inclusion and exclusion criteria of the study

Inclusion criteria	Exclusion criteria
Any of the following suspicious signs or symptoms of chronic knee PJI (more than 90 d), as following:	Acute signs or symptoms of knee infection (less than 90 d)
Persistent knee pain (more than 3 mo), without other apparent cause
Persistent joint effusion (more than 3 mo)
Persistent local heat (more than 3 mo)
Presence of draining sinus
Early failure of the prosthesis (less than 5 yr)
Radiographic findings suggesting infection[33]
Have not used antibiotics for at least 4 wk before the evaluation	Insufficient synovial fluid volume during knee aspiration
	Insufficient data for fulfilling the periprosthesis infection criteria[11]

PJI: Periprosthetic joint infection.

Table 2 Patient demographics

	Total	Aseptic cases	Infected cases	P value
n	53	31	22
Sex				0.221
Male	14 (26.4)	6 (19.4)	8 (36.4)
Female	39 (73.6)	25 (80.6)	14 (63.6)
Age (range)	68 (47-85)	67 (47-85)	70 (52-85)	0.302
Laterality				> 0.991
Right knee	28 (52.8)	16 (51.6)	12 (54.5)
Left knee	25 (47.2)	15 (48.4)	10 (45.5)
Inflammatory disease	12 (22.6)	7 (22.6)	5 (22.7)	> 0.991
RA	10 (18.9)	7 (22.6)	3 (13.6)
Gout	2 (3.8)	0	2 (9.1)
Sinus tract	4 (7.5)	0	4 (18.2)
Alpha-defensin S/CO	2.21 ± 2.73	0.28 ± 0.13	4.93 ± 2.28	< 0.013

¹Fisher's exact test.

²Unpaired t test.

³Mann-Whitney test. Values expressed in number (percentage). Age in years is presented as mean (range) and alpha-defensin S/CO in mean (standard deviation). RA: Rheumatoid arthritis.

Table 3 Statistical results of enzyme-linked immunosorbent assay and lateral flow test for all patients

	Aseptic	Infected	Sensitivity (95%CI)	Specificity (95%CI)	Accuracy (95%CI)
ELISA			95.5% (77.2%-99.9%)	100% (88.8%-100%)	98.1% (89.9%-100%)
Negative	31	1
Positive	0	21
Lateral flow			86.4% (65.1%-97.1%)	100% (88.8%-100%)	93.2% (82.8%-98.3%)
Negative	31	3
Positive	0	19

ELISA: Enzyme-linked immunosorbent assay.

Table 4 Statistical results of enzyme-linked immunosorbent assay and lateral flow test for patients without sinus tract

	Aseptic	Infected	Sensitivity (95%CI)	Specificity (95%CI)	Accuracy (95%CI)
ELISA			100% (81.5%-100%)	100% (88.8%-100%)	100% (92.8%-100%)
Negative	31	0
Positive	0	18
Lateral flow			100% (81.5%-100%)	100% (88.8%-100%)	100% (92.8%-100%)
Negative	31	0
Positive	0	18

ELISA: Enzyme-linked immunosorbent assay.