The Value Of Smear Microscopy Associating With MALDI-TOF MS In The Early Diagnosis And Treatment Of Lower Respiratory Tract Infection

Objective To evaluate the value of the technical identification results of matrix-assisted laser desorption and ionization time-of-flight mass spectrometry in smear microscopy of combined cultures of lower respiratory tract specimens for the early diagnosis and treatment of lower respiratory tract infections.Methods The lower respiratory tract specimens of 853 patients diagnosed with community-acquired bacterial lower respiratory tract infection from January 2019 to December 2021 were selected for culture,and the distribution of infected bacteria was counted.Selected lower respiratory tract specimens including sputum specimens and lavage samples,by comparing the two types of qualified rate and culture positive rate,and the qualified and unqualified specimens culture positive rate,microscopic results and compare the conformity rate,to evaluate whether different types of specimens,specimens are qualified for the diagnosis of pathogens.Through a retrospective study to compare whether the treatment is effective between the two groups of smear microscopy associating with MALDI-TOF MS identification results(combined identification results)with the use of antimicrobial drugs and compare the combination of antimicrobial identification results with body temperature,inflammation index,hospital days,hospitalization costs and prognosis,to evaluate the impact of the combination identification results and clinical antimicrobial use on patient prognosis.By comparing the number of hospitalization in the group of separate smear microscopy,MALDI-TOF MS identification and the combination results with the antimicrobial advantage,the diagnostic efficiency of the two identification methods was higher than that of use alone.Finally,the turnaround time(TAT)of MALDI-TOF MS identification and VITEK 2 biochemical identification was compared to evaluate the timeliness of smear microscopy associating with MALDI-TOF MS identification results.Results The distribution of infected bacteria was Gram positive coccus 12.02%(25/208),Gram negative bacilli 75.48%(157/208),and bacterial lower respiratory tract infections were mainly Gram negative bacilli.The qualified rate of lavage fluid group was higher than that of sputum samples,there are differences in comparison(P<0.01),and no statistical difference between the positive rate of the two groups(P>0.05).The positive rate of the qualified group,the conformity rate of the microscopic examination result and the appraisal result were higher than that of the unqualified group,there were differences in all the comparisons(P<0.05).The coincidence rate of the effective group microscopic examination result,the culture MALDI-TOF MS identification result,and the combination identification result with the dominant antimicrobial spectrum of using antimicrobial drugs were all significantly higher than that of the invalid group,there are differences in comparison(P<0.01).The number of hospitalization days and hospitalization cost of the group consistent with the dominant antibacterial spectrum were significantly less than that of the inconsistent group,and the prognosis was also better,there are differences in comparison(P<0.01).The body temperature of the group consistent with the superior antimicrobial spectrum,WBC count,CRP and SAA reduction were all more obvious in the inconsistent group.The hospitalization days and hospitalization cost were less than that of the inconsistent group,and the prognosis was better,and the comparison was different(P<0.05).The hospitalization days and the hospitalization costs were less than those of the separate smear microscopy results and the MALDI-TOF MS identification results(P<0.05).The MALDI-TOF MS identification report required significantly less TAT for sending the report than the TAT for VITEK 2 identification,and the comparison was different((P<0.01).Conclusion The pathogen distribution of bacterial sub-bacterial respiratory infection is mainly gram negative bacilli,and gradually mainly opportunistic pathogens.It is necessary to strengthen the rational use of antibiotics and strengthen the quality assurance before inspection.The two respiratory tract specimens in this study have different advantages and disadvantages for the diagnosis of pathogens and can be used in combination.Specimen smear microscopy can be used as a screening of specimen quality,and smear microscopy results can jointly guide the identification results of MALDI-TOF MS for early clinical diagnosis and treatment of lower respiratory tract infection.The combined results were used to diagnose more efficient than both identification results for diagnosis alone.Therefore,the identification results of smear microscopy associating with MALDI-TOF MS are very important for the early diagnosis and treatment of lower respiratory tract infection.