Different diagnostic properties of C-reactive protein, real-time PCR, and histopathology of frozen and permanent sections in diagnosis of periprosthetic joint infection

Figures & data

Table 1. Cases in which organisms were detected by culture, and the corresponding results regarding PCR, histopathology of frozen and paraffin sections, culture, and serum CRP preoperatively

Case	PCR result	Histopathology result		Culture result	Preoperative serum CRP
		frozen	paraffin
1	P	P	P	MRSA	19
2	P	N	P	MRSE	0.42
3	P	P	P	MRSA	21
4	P	N/A	P	Streptococcus	10
5	P	N/A	P	S. agalactiae	9.0
6	P	N/A	P	MSSA	17
7	P	P	P	Streptococcus	1.4
8	P	N	P	Streptococcus	1.5
9	P	P	P	MRSE	1.5
10	N	P	N	Peptostreptococcus	2.6

CRP: C-reactive protein;

MRSA: methicillin-resistant Staphylococcus aureus;

MRSE: methicillin-resistant Staphylococcus epidermidis;

MSSA: methicillin-sensitive Staphylococcus aureus;

N: negative; N/A: not applicable; P: positive;

PCR: polymerase chain reaction.

Table 2. Sensitivity, specificity, positive predictive value, and negative predictive value of preoperative serum CRP, PCR, and histopathology of frozen and paraffin sections

	Sensitivity (%)	Specificity (%)	Positive predictive value (%)	Negative predictive value (%)
CRP value (cutoff: 1.0)	90	85	45	98
Real-time PCR	90	45	19	97
Frozen sections	71	89	42	97
Paraffin sections	90	87	50	98

CRP: C-reactive protein; PCR: polymerase chain reaction.

Table 3. Likelihood ratio of positive test results (PLR), likelihood ratio of negative test results (NLR), diagnostic odds ratio, and 95% confidence interval (CI) for preoperative serum CRP value, PCR, and histopathology of frozen and paraffin sections

	PLR	NLR	Diagnostic odds ratio	95% CI
CRP value (cutoff, 1.0)	5.8	0.12	49	7–323
Real-time PCR	1.6	0.18	7	1.1–49
Frozen sections	6.6	0.32	20	4–109
Paraffin sections	7.1	0.11	62	9–414

For abbreviations, see Table 2.

Figure 1. A representative case with unclear infection (case 2). A. Preoperative plain radiograph. B. Plain radiograph after the first operation. Implant removal and antibiotic-loaded hydroxyapatite block replacement were performed. C. Plain radiograph after the second operation.

Figure 2. A representative case of periprosthetic joint infection (case 8). A. Preoperative plain radiograph, showing cup migration. B. Plain radiograph after the first operation. Implant removal and antibiotic-loaded hydroxyapatite block replacement were performed. C. Plain radiograph after the second operation.